Context: During meiosis, homologous chromosomes, one inherited from each parent, trade some of their alleles by crossing over. These homologous chromosomes and the alleles they carry are then distributed at random into gametes. Then, because myriad possible mating combinations exist in a population, fertilization brings together gametes that are likely to have different genetic backgrounds. The combined effects of these three mechanisms ensure that sexual reproduction rearranges existing alleles into fresh combinations each generation, providing much of the genetic variation that makes evolution possible.

Question: What would happen without crossing over?

Choices:
- A. homologous chromosomes would not trade some of their alleles
- B. homologous chromosomes would not carry alleles

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without fertilization?

Choices:
- A. gametes would not be brought together
- B. alleles would not be distributed at random into gametes

Prompt: Given the context, pick the right choice that answers the question


Question: What is the result of sexual reproduction?

Choices:
- A. rearrangement of alleles into fresh combinations
- B. crossing over

Prompt: Given the context, pick the right choice that answers the question


Context: When a molecule absorbs a photon of light, one of the molecule's electrons is elevated to an orbital where it has more potential energy. When the electron is in its normal orbital, the pigment molecule is said to be in its ground state. Absorption of a photon boosts an electron to an orbital of higher energy, and the pigment molecule is then said to be in an excited state. The only photons absorbed are those whose energy is exactly equal to the energy difference between the ground state and an excited state, and this energy difference varies from one kind of molecule to another.

Question: what would happen if an electron was not boosted?

Choices:
- A. the pigment molecule would not be in an excited state
- B. absorption of a photon would not occur

Prompt: Given the context, pick the right choice that answers the question


Question: What happens when a molecule absorbs a photon of light?

Choices:
- A. the pigment molecule goes to an excited state
- B. the pigment molecule goes to its ground state

Prompt: Given the context, pick the right choice that answers the question


Context: Abnormal changes on the cell surface cause cancer cells to lose attachments to neighboring cells and the extracellular matrix, allowing them to spread into nearby tissues. Cancer cells may also secrete signaling molecules that cause blood vessels to grow toward the tumor. A few tumor cells may separate from the original tumor, enter blood vessels and lymph vessels, and travel to other parts of the body. There, they may proliferate and form a new tumor. This spread of cancer cells to locations distant from their original site is called metastasis (see Figure 12.20).

Question: What can happen after cancer cells enter the blood vessels?

Choices:
- A. The cancer cells can proliferate and form a new tumor
- B. The cancer cells secrete signaling molecules

Prompt: Given the context, pick the right choice that answers the question


Question: What would necessarily not happen if cancer cells could not secrete signaling molecules?

Choices:
- A. Blood vessels will not grow toward the tumor
- B. The cancer cells will not enter the blood vessels

Prompt: Given the context, pick the right choice that answers the question


Question: How do cancer cells necessarily spread to distant tissues?

Choices:
- A. By entering blood vessels and lymph vessels
- B. By secreting signaling molecules

Prompt: Given the context, pick the right choice that answers the question


Question: New tumors are necessarily caused by the growth of blood vessels

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: During anaphase, MPF helps switch itself off by initiating a process that leads to the destruction of its own cyclin. The noncyclin part of MPF, the Cdk, persists in the cell, inactive until it becomes part of MPF again by associating with new cyclin molecules synthesized during the S and G2 phases of the next round of the cycle.

Question: How does Cdk become active?

Choices:
- A. Associating with cyclin
- B. Associating with MPF

Prompt: Given the context, pick the right choice that answers the question


Question: What is cyclin produced in S phase used for?

Choices:
- A. G2 phase
- B. Anaphase

Prompt: Given the context, pick the right choice that answers the question


Question: Cdk associates with MPF to become cyclin.

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without cyclin?

Choices:
- A. Cdk would not be synthesized
- B. MPF would always be switched off

Prompt: Given the context, pick the right choice that answers the question


Context: In E. coli, the process of cell division is initiated when the DNA of the bacterial chromosome begins to replicate at a specific place on the chromosome called the origin of replication, producing two origins. As the chromosome continues to replicate, one origin moves rapidly toward the opposite end of the cell (Figure 12.12). While the chromosome is replicating, the cell elongates. When replication is complete and the bacterium has reached about twice its initial size, its plasma membrane pinches inward, dividing the parent E. coli cell into two daughter cells.

Question: What initiates E.coli division?

Choices:
- A. DNA replication
- B. two daughter cells

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. Chromosome replication initiates, then the origins move to opposite ends of the cell.
- B. Origins move to opposite ends of the cell, then chromosome replication initiates.

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. Cell elongates, then the plasma membrane pinches inward, then two daughter cells are formed.
- B. Plasma membrane pinches inward, then the cell elongates, then two daughter cells are formed.

Prompt: Given the context, pick the right choice that answers the question


Question: Which events happen at the same time?

Choices:
- A. Cell elongation and plasma membrane pinching inward
- B. Cell elongation and chromosome replication

Prompt: Given the context, pick the right choice that answers the question


Question: Which events happen at the same time?

Choices:
- A. Chromosome replication and origin moving to the opposite end of the cell
- B. Origin moving to the opposite end of the cell and production of two origins

Prompt: Given the context, pick the right choice that answers the question


Question: What is caused by cell division in E. coli?

Choices:
- A. The bacterium has reached about twice its initial size.
- B. The parent E. coli is divided into two daughter cells.

Prompt: Given the context, pick the right choice that answers the question


Context: The actin microfilaments interact with the myosin molecules, causing the ring to contract. The contraction of the dividing cell's ring of microfilaments is like the pulling of a drawstring. The cleavage furrow deepens until the parent cell is pinched in two, producing two completely separated cells, each with its own nucleus and share of cytosol, organelles, and other subcellular structures.

Question: What would happen without actin microfilaments?

Choices:
- A. Each cell would not have myosin molecules
- B. The cleavage furrow would not deepen

Prompt: Given the context, pick the right choice that answers the question


Question: What do microfilament rings do?

Choices:
- A. separate the nucleus from the cytosol
- B. Pinch the parent cell in two

Prompt: Given the context, pick the right choice that answers the question


Question: The cleavage furrow creates actin microfilaments

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if the cleavage furrow did not deepen?

Choices:
- A. The nucleus of the parent cell would not be produced
- B. The parent cell would not divide

Prompt: Given the context, pick the right choice that answers the question


Context: Instead, during telophase, vesicles derived from the Golgi apparatus move along microtubules to the middle of the cell, where they coalesce, producing a cell plate (Figure 12.10b). Cell wall materials carried in the vesicles collect in the cell plate as it grows. The cell plate enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell. Two daughter cells result, each with its own plasma membrane. Meanwhile, a new cell wall arising from the contents of the cell plate has formed between the daughter cells.

Question: What would happen without vesicles from the Golgi apparatus?

Choices:
- A. Microtubules would not be produced
- B. A cell plate would not be produced

Prompt: Given the context, pick the right choice that answers the question


Question: The new cell wall forms the cell plate

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without microtubules?

Choices:
- A. The new cell wall would not be formed
- B. The vesicles from the Golgi apparatus would not be formed

Prompt: Given the context, pick the right choice that answers the question


Question: Cell wall materials produce the cell plate

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: A sudden change in the environment, such as a fire or flood, may drastically reduce the size of a population. A severe drop in population size can cause the bottleneck effect, so named because the population has passed through a "bottleneck" that reduces its size (Figure 23.10). By chance alone, certain alleles may be overrepresented among the survivors, others may be underrepresented, and some may be absent altogether. Ongoing genetic drift is likely to have substantial effects on the gene pool until the population becomes large enough that chance events have less impact.

Question: what is the result of a fire?

Choices:
- A. flood
- B. The bottleneck effect

Prompt: Given the context, pick the right choice that answers the question


Question: What is the end result of a flood?

Choices:
- A. Genetic drift
- B. The population becomes large

Prompt: Given the context, pick the right choice that answers the question


Question: What makes chance events have less impact?

Choices:
- A. The population becomes large
- B. The bottleneck effect

Prompt: Given the context, pick the right choice that answers the question


Question: What two events can happen at the same time?

Choices:
- A. Ongoing genetic drift and the population becomes large
- B. A severe drop in population and the bottleneck effect

Prompt: Given the context, pick the right choice that answers the question


Question: What is caused by flood?

Choices:
- A. The population becomes large
- B. genetic drift

Prompt: Given the context, pick the right choice that answers the question


Context: Nonkinetochore microtubules from opposite poles overlap each other extensively during metaphase (see Figure 12.8). During anaphase, the region of overlap is reduced as motor proteins attached to the microtubules walk them away from one another, using energy from ATP. As the microtubules push apart from each other, their spindle poles are pushed apart, elongating the cell. At the same time, the microtubules lengthen somewhat by the addition of tubulin subunits to their overlapping ends. As a result, the microtubules continue to overlap.

Question: What would happen without ATP?

Choices:
- A. Motor proteins would not walk away from one another
- B. Nonkinetochore microtubules would not overlap

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without motor proteins?

Choices:
- A. The cell would not elongate
- B. Microtubules would not overlap

Prompt: Given the context, pick the right choice that answers the question


Question: What allows microtubules to continue to overlap even though they are pushed apart?

Choices:
- A. microtubules lengthen
- B. Motor proteins walk away from one another

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without addition of tubulin subunits?

Choices:
- A. Motor proteins would not use energy from ATP
- B. Microtubules would not continue to overlap

Prompt: Given the context, pick the right choice that answers the question


Question: What directly pushes spindle poles apart?

Choices:
- A. Addition of tubulin subunits
- B. Microtubules pushing apart from each other

Prompt: Given the context, pick the right choice that answers the question


Context: The binding of signaling molecules to receptors is reversible. As the external concentration of signaling molecules falls, fewer receptors are bound at any given moment, and the unbound receptors revert to their inactive form. The cellular response occurs only when the concentration of receptors with bound signaling molecules is above a certain threshold. When the number of active receptors falls below that threshold, the cellular response ceases. Then, by a variety of means, the relay molecules return to their inactive forms: The GTPase activity intrinsic to a G protein hydrolyzes its bound GTP; the enzyme phosphodiesterase converts cAMP to AMP; protein phosphatases inactivate phosphorylated kinases and other proteins; and so forth.

Question: What happens when the external concentration of signaling molecules decreases below the threshold?

Choices:
- A. The cellular response will cease
- B. The cellular response will occur

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without receptors?

Choices:
- A. Cellular response ceases
- B. External concentration of signaling molecules stays above threshold

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. External concentration of signaling molecules falls, then number of active receptors falls
- B. External concentration of signaling molecules falls, then the cellular response occurs.

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. External concentration of signaling molecules falls below threshold, then GTPase hydrolyzes GTP
- B. External concentration of signaling molecules remains above threshold, then GTPase hydrolyzes GTP

Prompt: Given the context, pick the right choice that answers the question


Context: In one pathway, cyclic GMP, or cGMP, acts as a signaling molecule whose effects include relaxation of smooth muscle cells in artery walls. A compound that inhibits the hydrolysis of cGMP to GMP, thus prolonging the signal, was originally prescribed for chest pains because it increased blood flow to the heart muscle. Under the trade name Viagra, this compound is now widely used as a treatment for erectile dysfunction in human males. Because Viagra leads to dilation of blood vessels, it also allows increased blood flow to the penis, optimizing physiological conditions for penile erections.

Question: Hydrolysis of cGMP to GMP causes erections

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: Viagra inhibits hydrolysis of cGMP to GMP

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: Relaxation of smooth muscle in artery walls leads to increased blood flow

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without cGMP?

Choices:
- A. Increased blood flow to the heart muscle
- B. Erectile dysfunction occurs

Prompt: Given the context, pick the right choice that answers the question


Question: Which acts as a signaling molecule?

Choices:
- A. GMP
- B. cGMP

Prompt: Given the context, pick the right choice that answers the question


Context: The binding of a specific signaling molecule to a receptor in the plasma membrane triggers the first step in the chain of molecular interactions: the signal transduction pathway: that leads to a particular response within the cell. Like falling dominoes, the signal-activated receptor activates another molecule, which activates yet another molecule, and so on, until the protein that produces the final cellular response is activated.

Question: What would happen without the signal transduction pathway?

Choices:
- A. The cellular response would not be activated
- B. The receptor in the plasma membrane would not bind to signaling molecules

Prompt: Given the context, pick the right choice that answers the question


Question: What directly causes the final cellular response?

Choices:
- A. a protein
- B. signaling molecules

Prompt: Given the context, pick the right choice that answers the question


Context: Apoptosis is a type of programmed cell death in which cell components are disposed of in an orderly fashion, without damage to neighboring cells. Studies of the soil worm Caenorhabditis elegans showed that apoptosis occurs at defined times during embryonic development and clarified molecular details of the signaling pathway involved in the process. A protein (Ced-9) in the mitochondrial membrane acts as a brake; when released by a death signal, it allows activation of caspases, the main proteases that carry out apoptosis, and nucleases.

Question: Apoptosis damages neighboring cells

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: Without Ced-9, excessive apoptosis would occur

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: On what does Ced-9 act?

Choices:
- A. Nucleases and caspases
- B. the mitochondrial membrane

Prompt: Given the context, pick the right choice that answers the question


Question: Which is not a direct agent of apoptosis?

Choices:
- A. Ced-9
- B. Nucleases

Prompt: Given the context, pick the right choice that answers the question


Context: The scanning electron microscope (SEM) is especially useful for detailed study of the topography of a specimen (see Figure 6.3). The electron beam scans the surface of the sample, usually coated with a thin film of gold. The beam excites electrons on the surface, and these secondary electrons are detected by a device that translates the pattern of electrons into an electronic signal to a video screen. The result is an image of the specimen's surface that appears three-dimensional.

Question: An SEM emits a beam of secondary electrons

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. Secondary electrons are detected, the electron beam scans the sample, then the image is translated into a three-dimensional image
- B. Electron beam scans sample, secondary electrons are detected, then the image is translated into a three-dimensional image

Prompt: Given the context, pick the right choice that answers the question


Context: These data suggest that genetic drift during the bottleneck may have led to a loss of genetic variation and an increase in the frequency of harmful alleles.

Question: What causes a loss of genetic variation?

Choices:
- A. genetic drift
- B. harmful alleles

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without genetic drift?

Choices:
- A. no loss of genetic variation
- B. an increase in the frequency of harmful alleles

Prompt: Given the context, pick the right choice that answers the question


Context: The transmission electron microscope (TEM) is used to study the internal structure of cells (see Figure 6.3). The TEM aims an electron beam through a very thin section of the specimen, similar to the way a light microscope transmits light through a slide. The specimen has been stained with atoms of heavy metals, which attach to certain cellular structures, thus enhancing the electron density of some parts of the cell more than others. The electrons passing through the specimen are scattered more in the denser regions, so fewer are transmitted. The image displays the pattern of transmitted electrons. Instead of using glass lenses, the TEM uses electromagnets as lenses to bend the paths of the electrons, ultimately focusing the image onto a monitor for viewing.

Question: The TEM uses what?

Choices:
- A. an electron beam
- B. a light microscope

Prompt: Given the context, pick the right choice that answers the question


Question: what do atoms of heavy metals do?

Choices:
- A. use electromagnets
- B. enhance electron density of some parts of the cell more than others

Prompt: Given the context, pick the right choice that answers the question


Context: A cell is frozen and fractured with a knife. The fracture plane often follows the hydrophobic interior of a membrane, splitting the phospholipid bilayer into two separated layers. Each membrane protein goes wholly with one of the layers.

Question: Each membrane protein is fractured

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What entity fractures the cell?

Choices:
- A. The hyrdophobic interior
- B. a knife

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if the phospholipid bilayer was not split into two separated layers?

Choices:
- A. the cell would not be frozen
- B. Each membrane protein would not go wholly with one of the layers

Prompt: Given the context, pick the right choice that answers the question


Context: A cell such as an amoeba crawls along a surface by extending cellular extensions called pseudopodia (from the Greek  pseudes, false, and pod, foot), and moving toward them. Pseudopodia extend by assembly of actin subunits into microfilament networks that convert cytoplasm from a sol to a gel inside these cell projections. Cell surface proteins on the pseudopodium make strong attachments to the "road." Next, the interaction of microfilaments with myosin near the cell's trailing end causes contraction of that region, loosening its cell-surface attachments and pulling it forward toward the pseudopodia.

Question: What converts cytoplasm from a sol to a gel?

Choices:
- A. microfilament networks
- B. pseudopodia

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without cell surface proteins?

Choices:
- A. actin subunits could not assemble into microfilament networks
- B. The amoeba could not crawl along a surface

Prompt: Given the context, pick the right choice that answers the question


Question: Cytoplasm is converted from a sol to a gel inside pseudopodia

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: NADH and FADH2 transfer electrons to the electron transport chain. Electrons move down the chain, losing energy in several energy-releasing steps. Finally, electrons are passed to O2, reducing it to H2O.

Question: What reduces O2?

Choices:
- A. H2O
- B. electrons

Prompt: Given the context, pick the right choice that answers the question


Question: NADH and FADH2 lose energy in several energy-releasing steps

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: In 1795, Scottish geologist James Hutton (1726-1797) proposed that Earth's geologic features could be explained by gradual mechanisms still operating today. For example, he suggested that valleys were often formed by rivers wearing through rocks and that rocks containing marine fossils were formed when sediments that had eroded from the land were carried by rivers to the sea, where they buried dead marine organisms.The leading geologist of Darwin's time, Charles Lyell (1797-1875), incorporated Hutton's thinking into his principle of uniformitarianism, which stated that mechanisms of change are constant over time. Lyell proposed that the same geologic processes are operating today as in the past, and at the same rate.

Question: How were valleys formed?

Choices:
- A. rivers wearing through rocks
- B. rocks containing marine fossils

Prompt: Given the context, pick the right choice that answers the question


Question: How were rocks containing marine fossils formed?

Choices:
- A. sediments eroded from the land were carried by rivers to the sea
- B. rivers wearing through rocks

Prompt: Given the context, pick the right choice that answers the question


Context: Organisms share many characteristics, leading Darwin to perceive unity in life. He attributed the unity of life to the descent of all organisms from an ancestor that lived in the remote past. He also thought that as the descendants of that ancestral organism lived in various habitats over millions of years, they accumulated diverse modifications, or adaptations, that fit them to specific ways of life. Darwin reasoned that over long periods of time, descent with modification eventually led to the rich diversity of life we see today.

Question: What lead Darwin to perceive unity in life?

Choices:
- A. organisms share many characteristics
- B. The remote past

Prompt: Given the context, pick the right choice that answers the question


Question: What caused adaptations?

Choices:
- A. the remote past
- B. various habitats

Prompt: Given the context, pick the right choice that answers the question


Question: What does descent with modification eventually lead to?

Choices:
- A. rich diversity of life
- B. long periods of time

Prompt: Given the context, pick the right choice that answers the question


Context: Darwin reasoned that if artificial selection can bring about dramatic change in a relatively short period of time, then natural selection should be capable of substantial modification of species over many hundreds of generations. Even if the advantages of some heritable traits over others are slight, the advantageous variations will gradually accumulate in the population, and less favorable variations will diminish. Over time, this process will increase the frequency of individuals with favorable adaptations and hence refine the match between organisms and their environment (see Figure 1.20).

Question: Advantageous variations and less favorable variations will diminish

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without natural selection?

Choices:
- A. Artificial selection would not bring about dramatic change in a relatively short period of time
- B. substantial modifications of species over many hundreds of generations would not occur

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following is caused by the increased frequency of individuals with favorable adaptations?

Choices:
- A. artificial selection
- B. refined match between organisms and their environment

Prompt: Given the context, pick the right choice that answers the question


Context: For example, suppose that near our original hypothetical wildflower population there is another population consisting primarily of white-flowered individuals (CWCW). Insects carrying pollen from these plants may fly to and pollinate plants in our original population. The introduced CW alleles would modify our original population's allele frequencies in the next generation. Because alleles are exchanged between populations, gene flow tends to reduce the genetic differences between populations. In fact, if it is extensive enough, gene flow can result in two populations combining into a single population with a common gene pool.

Question: What is the result of gene flow?

Choices:
- A. reduced genetic differences between populations
- B. Insects carry pollen

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. Alleles are exchanged between populations, then gene flow reduces genetic differences between populations, then two populations combine into a single population
- B. Alleles are exchanged between populations, then two populations combine into a single population, then gene flow reduces genetic differences between populations

Prompt: Given the context, pick the right choice that answers the question


Question: Extensive gene flow can result in a common gene pool.

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: The story begins in 1943, when penicillin became the first widely used antibiotic. Since then, penicillin and other antibiotics have saved millions of lives. However, by 1945, more than 20% of the S. aureus strains seen in hospitals were already resistant to penicillin. These bacteria had an enzyme, penicillinase, that could destroy penicillin. Researchers responded by developing antibiotics that were not destroyed by penicillinase, but some S. aureus populations developed resistance to each new drug within a few years. In 1959, doctors began using the powerful antibiotic methicillin, but within two years, methicillin-resistant strains of S. aureus appeared.

Question: What entity destroys penicillin?

Choices:
- A. penicillinase
- B. Hospitals

Prompt: Given the context, pick the right choice that answers the question


Question: Each new drug was what?

Choices:
- A. Developed by researchers
- B. destroyed by penicillinase

Prompt: Given the context, pick the right choice that answers the question


Context: Also, the development of newer sequencing techniques, generally called sequencing by synthesis (see Chapter 20), has resulted in massive increases in speed and decreases in the cost of sequencing entire genomes. In these new techniques, many very small fragments (fewer than 100 base pairs) are sequenced at the same time, and computer software rapidly assembles the complete sequence. Because of the sensitivity of these techniques, the fragments can be sequenced directly; the cloning step (stage ➋ in Figure 21.3) is unnecessary.

Question: What has caused massive increases in speed and decreases in the cost of sequencing?

Choices:
- A. entire genomes
- B. sequencing by synthesis

Prompt: Given the context, pick the right choice that answers the question


Question: What are sequenced?

Choices:
- A. very small fragments
- B. new techniques

Prompt: Given the context, pick the right choice that answers the question


Question: What is required for sequencing?

Choices:
- A. the cloning step
- B. fragments

Prompt: Given the context, pick the right choice that answers the question


Context: By a similar process, a particular exon within a gene could be duplicated on one chromosome and deleted from the other. The gene with the duplicated exon would code for a protein containing a second copy of the encoded domain. This change in the protein's structure could augment its function by increasing its stability, enhancing its ability to bind a particular ligand, or altering some other property.

Question: What entity could be duplicated?

Choices:
- A. a gene
- B. a particular exon

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if a particular exon within a gene was not duplicated on one chromosome and deleted from another?

Choices:
- A. the protein would not be able to bind a particular ligand
- B. The gene with the duplicated exon would not code for a protein containing a second copy of the encoded domain

Prompt: Given the context, pick the right choice that answers the question


Context: When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population; this is called the founder effect. The founder effect might occur, for example, when a few members of a population are blown by a storm to a new island. Genetic drift, in which chance events alter allele frequencies, will occur in such a case if the storm indiscriminately transports some individuals (and their alleles), but not others, from the source population. The founder effect probably accounts for the relatively high frequency of certain inherited disorders among isolated human populations.

Question: Which event occurs first?

Choices:
- A. the smaller group may establish a new population
- B. a few individuals become isolated from a larger population

Prompt: Given the context, pick the right choice that answers the question


Question: Genetic drift describes what process?

Choices:
- A. chance events alter allele frequencies
- B. the founder effect

Prompt: Given the context, pick the right choice that answers the question


Question: What is the result of the founder effect?

Choices:
- A. the storm indiscriminately transports some individuals
- B. a new population whose gene pool differs from the source population

Prompt: Given the context, pick the right choice that answers the question


Context: Millions of greater prairie chickens (Tympanuchus cupido) once lived on the prairies of Illinois. As these prairies were converted to farmland and other uses during the 19th and 20th centuries, the number of greater prairie chickens plummeted (Figure 23.11a). By 1993, only two Illinois populations remained, which together harbored fewer than 50 birds. The few surviving birds had low levels of genetic variation, and less than 50% of their eggs hatched, compared with much higher hatching rates of the larger populations in Kansas and Nebraska (Figure 23.11b). These data suggest that genetic drift during the bottleneck may have led to a loss of genetic variation and an increase in the frequency of harmful alleles.

Question: What is the result of genetic drift?

Choices:
- A. less than 50% of the eggs hatched
- B. the bottleneck

Prompt: Given the context, pick the right choice that answers the question


Context: Thus, as predicted, drift had reduced the genetic variation of the small 1993 population. Drift may also have increased the frequency of harmful alleles, leading to the low egg-hatching rate. To counteract these negative effects, 271 birds from neighboring states were added to the Illinois population over four years. This strategy succeeded: New alleles entered the population, and the egg-hatching rate improved to over 90%. Overall, studies on the Illinois greater prairie chicken illustrate the powerful effects of genetic drift in small populations and provide hope that in at least some populations, these effects can be reversed.

Question: what was the result of drift?

Choices:
- A. New alleles entered the population
- B. the low egg-hatching rate

Prompt: Given the context, pick the right choice that answers the question


Question: What was the result of new alleles entering the population?

Choices:
- A. the egg-hatching rate improved
- B. 271 birds from neighboring states were added

Prompt: Given the context, pick the right choice that answers the question


Question: genetic drift can be reversed

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if 271 birds from neighboring states were not added?

Choices:
- A. New alleles would not have entered the population
- B. genetic drift would not have occured

Prompt: Given the context, pick the right choice that answers the question


Context: Finally, gene flow has become an increasingly important agent of evolutionary change in human populations. Humans today move much more freely about the world than in the past. As a result, mating is more common between members of populations that previously had very little contact, leading to an exchange of alleles and fewer genetic differences between those populations.

Question: Gene flow causes what?

Choices:
- A. Humans today move much more freely about the world
- B. fewer differences between populations

Prompt: Given the context, pick the right choice that answers the question


Question: What happens because mating is more common between members of populations that previously had very little contact?

Choices:
- A. humans today move much more freely
- B. fewer genetic differences between those populations

Prompt: Given the context, pick the right choice that answers the question


Context: Stabilizing selection (Figure 23.13c) acts against both extreme phenotypes and favors intermediate variants. This mode of selection reduces variation and tends to maintain the status quo for a particular phenotypic character. For example, the birth weights of most human babies lie in the range of 3-4 kg (6.6-8.8 pounds); babies who are either much smaller or much larger suffer higher rates of mortality.

Question: Stabilizing selection results in what?

Choices:
- A. extreme phenotypes
- B. intermediate variants

Prompt: Given the context, pick the right choice that answers the question


Question: Human babies that in the range of 3-4 kg suffer higher rates of mortality

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: If individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes, they exhibit heterozygote advantage. In such a case, natural selection tends to maintain two or more alleles at that locus.

Question: If individuals exhibit heterozygote advantage at a particular locus, natural selection tends to maintain two or more alleles at that locus

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What is required for heterozygote advantage?

Choices:
- A. natural selection
- B. individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes

Prompt: Given the context, pick the right choice that answers the question


Context: Because biological species are defined in terms of reproductive compatibility, the formation of a new species hinges on reproductive isolation: the existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring. Such barriers block gene flow between the species and limit the formation of hybrids, offspring that result from an interspecific mating. Although a single barrier may not prevent all gene flow, a combination of several barriers can effectively isolate a species' gene pool.

Question: what is required for the formation of a new species?

Choices:
- A. reproductive isolation
- B. reproductive compatibility

Prompt: Given the context, pick the right choice that answers the question


Question: producing viable, fertile offspring requires the formation of a new species

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What most effectively prevents all gene flow?

Choices:
- A. a combination of several barriers
- B. a single barrier

Prompt: Given the context, pick the right choice that answers the question


Context: A second form of polyploidy can occur when two different species interbreed and produce hybrid offspring. Most such hybrids are sterile because the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species. However, an infertile hybrid may be able to propagate itself asexually (as many plants can do). In subsequent generations, various mechanisms can change a sterile hybrid into a fertile polyploid called an allopolyploid (Figure 24.11).

Question: What is the final result of an infertile hybrid propagating itself asexually?

Choices:
- A. other species
- B. an allopolyploid

Prompt: Given the context, pick the right choice that answers the question


Question: Why are most hybrids sterile?

Choices:
- A. various mechanisms can change a sterile hybrid into a fertile polyploid
- B. meiosis is prevented

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if the set of chromosomes could pair during meiosis with the set of chromosomes from the other species?

Choices:
- A. most hybrids would not be sterile
- B. hybrid offspring would not be produced

Prompt: Given the context, pick the right choice that answers the question


Context: When hybrids are less fit than members of their parent species, as in the Bombina example, we might expect natural selection to strengthen prezygotic barriers to reproduction, thus reducing the formation of unfit hybrids. Because this process involves reinforcing reproductive barriers, it is called reinforcement. If reinforcement is occurring, a logical prediction is that barriers to reproduction between species should be stronger for sympatric populations than for allopatric populations.

Question: What is required for reinforcement?

Choices:
- A. hybrids are less fit than members of their parent species
- B. the Bombina example

Prompt: Given the context, pick the right choice that answers the question


Question: Reinforcement creates stronger barriers to reproduction in which populations?

Choices:
- A. allopatric
- B. sympatric

Prompt: Given the context, pick the right choice that answers the question


Question: Reinforcement does what?

Choices:
- A. strengthens prezygotic barriers to reproduction
- B. formation of unfit hybrids

Prompt: Given the context, pick the right choice that answers the question


Context: Next let's consider the case in which two species contact one another in a hybrid zone, but the barriers to reproduction are not strong. So much gene flow may occur that reproductive barriers weaken further and the gene pools of the two species become increasingly alike. In effect, the speciation process reverses, eventually causing the two hybridizing species to fuse into a single species.

Question: If the speciation process reverses, what is the result?

Choices:
- A. two hybridizing species
- B. a single species

Prompt: Given the context, pick the right choice that answers the question


Question: what would happen if two species did not contact one another in a hybrid zone?

Choices:
- A. gene flow would not occur
- B. The speciation process would not occur

Prompt: Given the context, pick the right choice that answers the question


Question: What is caused by the reversal of the speciation process?

Choices:
- A. two hybridizing species
- B. a single species

Prompt: Given the context, pick the right choice that answers the question


Context: They hypothesize that chemical and physical processes on early Earth, aided by the emerging force of natural selection, could have produced very simple cells through a sequence of four main stages: The abiotic (nonliving) synthesis of small organic molecules, such as amino acids and nitrogenous bases The joining of these small molecules into macromolecules, such as proteins and nucleic acids The packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings The origin of self-replicating molecules that eventually made inheritance possible

Question: Which event occurred first?

Choices:
- A. production of very simple cells
- B. synthesis of small organic molecules

Prompt: Given the context, pick the right choice that answers the question


Question: protocells do what?

Choices:
- A. maintain an internal chemistry different from that of their surroundings
- B. abiotic synthesis of small organic molecules

Prompt: Given the context, pick the right choice that answers the question


Question: What is required for inheritance?

Choices:
- A. their surroundings
- B. self-replicating molecules

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following happened first?

Choices:
- A. very simple cells were produced
- B. The joining of small molecules into macromolecules

Prompt: Given the context, pick the right choice that answers the question


Context: The term refers to the last stage of infection, during which the bacterium lyses (breaks open) and releases the phages that were produced within the cell. Each of these phages can then infect a healthy cell, and a few successive lytic cycles can destroy an entire bacterial population in just a few hours.

Question: What is the direct result of lysing?

Choices:
- A. Phages are released
- B. Infection of a healthy cell

Prompt: Given the context, pick the right choice that answers the question


Question: Phages are produced during lysing

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: Though we usually cannot date these old fossils directly, an indirect method can be used to infer the age of fossils that are sandwiched between two layers of volcanic rocks. As lava cools into volcanic rock, radioisotopes from the surrounding environment become trapped in the newly formed rock. Some of the trapped radioisotopes have long half-lives, allowing geologists to estimate the ages of ancient volcanic rocks.

Question: What would happen if the trapped radioisotopes did not have long half-lives?

Choices:
- A. radioisotopes from the surrounding environment would not become trapped in the newly formed rock
- B. geologists could not estimate the ages of ancient volcanic rocks

Prompt: Given the context, pick the right choice that answers the question


Question: What is required to estimate the ages of ancient volcanic rock?

Choices:
- A. radioisotopes
- B. old fossils

Prompt: Given the context, pick the right choice that answers the question


Context: The amount of atmospheric O2 increased gradually from about 2.7 to 2.3 billion years ago, but then shot up relatively rapidly to between 1% and 10% of its present level (Figure 25.8). This "oxygen revolution" had an enormous impact on life. In certain of its chemical forms, oxygen attacks chemical bonds and can inhibit enzymes and damage cells. As a result, the rising concentration of atmospheric O2 probably doomed many prokaryotic groups.

Question: The increase of atmospheric O2 produced what?

Choices:
- A. an enormous impact on life
- B. many prokaryotic groups

Prompt: Given the context, pick the right choice that answers the question


Context: Hundreds of different restriction enzymes have been identified and isolated. Each restriction enzyme is very specific, recognizing a particular short DNA sequence, or restriction site, and cutting both DNA strands at precise points within this restriction site. The DNA of a bacterial cell is protected from the cell's own restriction enzymes by the addition of methyl groups (CH3) to adenines or cytosines within the sequences recognized by the enzymes.

Question: Restriction enzymes do what?

Choices:
- A. Cut both DNA strands at precise points
- B. protect the DNA of a bacterial cell

Prompt: Given the context, pick the right choice that answers the question


Question: What protects the DNA of a bacterial cell?

Choices:
- A. methyl groups
- B. the cell's own restriction enzymes

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without restriction sites?

Choices:
- A. DNA strands would not be cut
- B. Hundreds of different restriction enzymes would not have been identified and isolated

Prompt: Given the context, pick the right choice that answers the question


Context: The restriction enzyme in this example (called EcoRI) recognizes a specific six-base-pair sequence, the restriction site, and makes staggered cuts in the sugar-phosphate backbones within this sequence, producing fragments with sticky ends. Any fragments with complementary sticky ends can base-pair, including the two original fragments. If the fragments come from different DNA molecules, the ligated product is recombinant DNA.

Question: EcoRI does what?

Choices:
- A. makes staggered cuts
- B. comes from different DNA molecules

Prompt: Given the context, pick the right choice that answers the question


Question: The restriction enzyme in this example produces fragments with sticky ends

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without sticky ends?

Choices:
- A. fragments could not base-pair
- B. EcoRI would not recognize a specific sequence

Prompt: Given the context, pick the right choice that answers the question


Context: After HIV enters a host cell, its reverse transcriptase molecules are released into the cytoplasm, where they catalyze synthesis of viral DNA. The newly made viral DNA then enters the cell's nucleus and integrates into the DNA of a chromosome. The integrated viral DNA, called a provirus, never leaves the host's genome, remaining a permanent resident of the cell. (Recall that a prophage, in contrast, leaves the host's genome at the start of a lytic cycle.) The host's RNA polymerase transcribes the proviral DNA into RNA molecules, which can function both as mRNA for the synthesis of viral proteins and as genomes for the new viruses that will be assembled and released from the cell.

Question: What produces viral DNA?

Choices:
- A. cytoplasm
- B. reverse transcriptase molecules

Prompt: Given the context, pick the right choice that answers the question


Question: Which entity is part of HIV?

Choices:
- A. Prophage
- B. Provirus

Prompt: Given the context, pick the right choice that answers the question


Question: What can RNA become?

Choices:
- A. A provirus
- B. Genomes for the new viruses

Prompt: Given the context, pick the right choice that answers the question


Question: What is required to make mRNA?

Choices:
- A. RNA polymerase
- B. A prophage

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without RNA molecules?

Choices:
- A. synthesis of viral proteins would not occur
- B. RNA polymerase would not transcribe proviral DNA

Prompt: Given the context, pick the right choice that answers the question


Context: Bacterial plasmids are widely used as cloning vectors for several reasons: They can be readily obtained from commercial suppliers, manipulated to form recombinant plasmids by insertion of foreign DNA in vitro, and then introduced into bacterial cells. Moreover, recombinant bacterial plasmids (and the foreign DNA they carry) multiply rapidly owing to the high reproductive rate of their host cells.

Question: Recombinant bacterial plasmids carry foreign DNA

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: ➋ Both the plasmid and the hummingbird DNA are cut with the same restriction enzyme, and then ➌ the fragments are mixed together, allowing base pairing between their complementary sticky ends. We then add DNA ligase, which covalently bonds the sugar-phosphate backbones of the fragments whose sticky ends have base-paired.

Question: What cuts the plasmid?

Choices:
- A. a restriction enzyme
- B. the hummingbird DNA

Prompt: Given the context, pick the right choice that answers the question


Question: What does DNA ligase do?

Choices:
- A. allows base pairing between complementary sticky ends
- B. covalently bonds the sugar-phosphate backbones of the fragments

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without sticky ends?

Choices:
- A. DNA ligase would covalently bond the sugar-phosphate backbones of the fragments
- B. the hummingbird DNA would not be cut

Prompt: Given the context, pick the right choice that answers the question


Context: ➍ The DNA mixture is then added to bacteria that have a mutation in the lacZ gene on their own chromosome, making them unable to hydrolyze lactose or X-gal. Under suitable experimental conditions, the cells take up foreign DNA by transformation (see p. 306). Some cells acquire a recombinant plasmid carrying a gene, while others may take up a nonrecombinant plasmid, a fragment of noncoding hummingbird DNA, or nothing at all.

Question: The foreign DNA does what?

Choices:
- A. makes bacteria unable to hydrolyze lactose or X-gal
- B. Is taken up by transformation

Prompt: Given the context, pick the right choice that answers the question


Question: What can the bacteria do?

Choices:
- A. hydrolyze lactose or X-gal
- B. acquire a recombinant plasmid

Prompt: Given the context, pick the right choice that answers the question


Question: Some cells may take up nothing at all

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: ➎ First, plating out all the bacteria on solid nutrient medium containing ampicillin allows us to distinguish the cells that have taken up plasmids, whether recombinant or not, from the other cells. Under these conditions, only cells with a plasmid will reproduce because only they have the ampR gene conferring resistance to the ampicillin in the medium. Each reproducing bacterium forms a clone of cells. Once the clone contains between 105 and 108 cells, it is visible as a mass, or colony, on the agar. As cells reproduce, any foreign genes carried by recombinant plasmids are also copied (cloned).

Question: Which event occurs first?

Choices:
- A. a clone of cells is formed
- B. plating out all the bacteria

Prompt: Given the context, pick the right choice that answers the question


Question: What does the ampR gene do?

Choices:
- A. forms a clone of cells
- B. confers resistance to the ampicillin in the medium

Prompt: Given the context, pick the right choice that answers the question


Question: What happens because reproducing bacteria form clones of cells?

Choices:
- A. Any foreign genes carried by recombinant plasmids are also copied
- B. The ampR gene will confer resistance to the ampicillin in the medium

Prompt: Given the context, pick the right choice that answers the question


Context: Figure 20.6 Making complementary DNA (cDNA) from eukaryotic genes. Complementary DNA is DNA made in vitro using mRNA as a template for the first strand. Because the mRNA contains only exons, the resulting double-stranded cDNA carries the complete coding sequence of the gene but no introns. Although only one mRNA is shown here, the final collection of cDNAs would reflect all the mRNAs that were present in the cell.

Question: mRNA is made in vitro

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: cDNA carries what?

Choices:
- A. the complete coding sequence of the gene
- B. introns

Prompt: Given the context, pick the right choice that answers the question


Question: Why does the cDNA carry the complete coding sequence but no introns?

Choices:
- A. The DNA is made in vitro
- B. The mRNA contains only exons

Prompt: Given the context, pick the right choice that answers the question


Context: Such researchers can make another kind of DNA library by starting with fully processed mRNA extracted from cells where the gene is expressed (Figure 20.6). The enzyme reverse transcriptase (obtained from retroviruses) is used in vitro to make a single-stranded DNA reverse transcript of each mRNA molecule. Recall that the 3' end of the mRNA has a stretch of adenine (A) ribonucleotides called a poly-A tail. This feature allows use of a short strand of thymine deoxyribonucleotides (dT's) as a primer for the reverse transcriptase. Following enzymatic degradation of the mRNA, a second DNA strand, complementary to the first, is synthesized by DNA polymerase. The resulting double-stranded DNA is called complementary DNA (cDNA).

Question: What would happen without reverse transcriptase?

Choices:
- A. mRNA would not be produced
- B. single-stranded DNA would not be produced

Prompt: Given the context, pick the right choice that answers the question


Question: Which event occurs first?

Choices:
- A. cDNA is produced
- B. enzymatic degradation of mRNA

Prompt: Given the context, pick the right choice that answers the question


Question: What is eventually produced by the enzymatic degradation of the mRNA?

Choices:
- A. DNA polymerase
- B. cDNA

Prompt: Given the context, pick the right choice that answers the question


Context: Recall that the clones in our hummingbird genomic library have been stored in a multiwell plate (see Figure 20.5c). If we transfer a few cells from each well to a defined location on a membrane made of nylon or nitrocellulose, we can screen a large number of clones simultaneously for the presence of DNA complementary to our DNA probe (Figure 20.7).

Question: What is transferred to a defined location on a membrane?

Choices:
- A. a few cells from each well
- B. our hummingbird genomic library

Prompt: Given the context, pick the right choice that answers the question


Context: By using probes with different nucleotide sequences in different experiments, researchers can screen the collection of bacterial clones for different genes. After we've identified the location of a clone carrying the beta-globin gene, we can grow some cells from that colony in liquid culture in a large tank and then easily isolate many copies of the gene for our studies. We can also use the cloned gene as a probe to identify similar or identical genes in DNA from other sources, such as other species of birds.

Question: What is the result of liquid culture?

Choices:
- A. identifying the location of a clone
- B. growing cells

Prompt: Given the context, pick the right choice that answers the question


Question: What will happen if we do not identify the location of a clone carrying the beta-globulin gene?

Choices:
- A. We cannot isolate many copies of the gene
- B. We cannot use probes with different nucleotide sequences

Prompt: Given the context, pick the right choice that answers the question


Context: To overcome differences in promoters and other DNA control sequences, scientists usually employ an expression vector, a cloning vector that contains a highly active bacterial promoter just upstream of a restriction site where the eukaryotic gene can be inserted in the correct reading frame. The bacterial host cell will recognize the promoter and proceed to express the foreign gene now linked to that promoter. Such expression vectors allow the synthesis of many eukaryotic proteins in bacterial cells.

Question: Which event occurs first?

Choices:
- A. the bacterial host will express the foreign gene
- B. the eukaryotic gene is inserted in the correct reading frame

Prompt: Given the context, pick the right choice that answers the question


Question: The promoter expresses the foreign gene

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What is eventually synthesized because the bacterial host cell will recognize the promoter?

Choices:
- A. An expression vector
- B. Many eukaryotic proteins

Prompt: Given the context, pick the right choice that answers the question


Context: In electroporation, a brief electrical pulse applied to a solution containing cells creates temporary holes in their plasma membranes, through which DNA can enter. (This technique is now commonly used for bacteria as well. )

Question: DNA does what?

Choices:
- A. Is used for bacteria
- B. enters through temporary holes in plasma membranes

Prompt: Given the context, pick the right choice that answers the question


Question: What creates temporary holes in the plasma membranes?

Choices:
- A. DNA
- B. a brief electrical pulse

Prompt: Given the context, pick the right choice that answers the question


Context: Occasional errors during PCR replication impose limits on the number of good copies that can be made by this method. When PCR is used to provide the specific DNA fragment for cloning, the resulting clones are sequenced to select clones with error-free inserts. PCR errors also impose limits on the length of DNA fragments that can be copied.

Question: PCR errors limit what?

Choices:
- A. sequencing
- B. the length of DNA fragments that can be copied

Prompt: Given the context, pick the right choice that answers the question


Question: Sequencing produces error-free inserts

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: Many approaches for studying DNA molecules involve gel electrophoresis. This technique uses a gel made of a polymer, such as the polysaccharide agarose. The gel acts as a molecular sieve to separate nucleic acids or proteins on the basis of size, electrical charge, and other physical properties (Figure 20.9). Because nucleic acid molecules carry negative charges on their phosphate groups, they all travel toward the positive pole in an electric field. As they move, the thicket of agarose fibers impedes longer molecules more than it does shorter ones, separating them by length. Thus, gel electrophoresis separates a mixture of linear DNA molecules into bands, each band consisting of many thousands of DNA molecules of the same length.

Question: Polysaccharide agarose does what?

Choices:
- A. studies DNA molecules
- B. acts as a molecular sieve

Prompt: Given the context, pick the right choice that answers the question


Question: Nucleic acid molecules do what?

Choices:
- A. impede longer molecules
- B. move toward the positive pole

Prompt: Given the context, pick the right choice that answers the question


Question: What happens because longer molecules are impeded more than shorter ones?

Choices:
- A. nucleic acid molecules carry negative charges on their phosphate groups
- B. a mixture of linear DNA molecules is separated into bands

Prompt: Given the context, pick the right choice that answers the question


Context: Gel electrophoresis separates macromolecules on the basis of their rate of movement through an agarose gel in an electric field: The distance a DNA molecule travels is inversely proportional to its length. A mixture of DNA molecules, usually fragments produced by restriction enzyme digestion (cutting) or PCR amplification, is separated into bands. Each band contains thousands of molecules of the same length. Results After the current is turned off, a DNA-binding dye (ethidium bromide) is added. This dye fluoresces pink in ultraviolet light, revealing the separated bands to which it binds.

Question: Ethidium bromide does what?

Choices:
- A. turns the current off
- B. reveals separated bands

Prompt: Given the context, pick the right choice that answers the question


Question: Macromolecules move through an agarose gel

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without a DNA-binding dye?

Choices:
- A. separated bands would not be revealed
- B. The current would not be turned off

Prompt: Given the context, pick the right choice that answers the question


Context: The sequence of nucleotides in any cloned DNA fragment of up to 800-1,000 base pairs in length can be determined rapidly with machines that carry out sequencing reactions and separate the labeled reaction products by length. Technique This method synthesizes a set of DNA strands complementary to the original DNA fragment.  Each strand starts with the same primer and ends with a dideoxyribonucleotide (ddNTP), a modified nucleotide. Incorporation of a ddNTP terminates a growing DNA strand because it lacks a 3' OH group, the site for attachment of the next nucleotide (see Figure 16.14). In the set of strands synthesized, each nucleotide position along the original sequence is represented by strands ending at that point with the complementary ddNTP. Because each type of ddNTP is tagged with a distinct fluorescent label, the identity of the ending nucleotides of the new strands, and ultimately the entire original sequence, can be determined.

Question: What does ddNTP do?

Choices:
- A. attachment of the next nucleotide
- B. terminates a growing DNA strand

Prompt: Given the context, pick the right choice that answers the question


Question: ddNTP is required to determine the entire original sequence

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What will not happen without a distinct fluorescent label?

Choices:
- A. each nucleotide position along the original sequence is not represented by strands ending at that point with the complementary ddNT
- B. The entire nucleotide can not be determined

Prompt: Given the context, pick the right choice that answers the question


Context: Having cloned a given gene, researchers can make labeled nucleic acid probes that will hybridize with mRNAs transcribed from the gene. The probes can provide information about when or where in the organism the gene is transcribed. Transcription levels are commonly used as a measure of gene expression.

Question: What is required to make labeled nucleic acid probes?

Choices:
- A. having cloned a given gene
- B. mRNAs

Prompt: Given the context, pick the right choice that answers the question


Question: What is enabled using the information of about when and where the gene is transcribed?

Choices:
- A. The probes
- B. a measure of gene expression

Prompt: Given the context, pick the right choice that answers the question


Context: The first is called Northern blotting (a play on words based on this method's close similarity to Southern blotting). In this method, we carry out gel electrophoresis on samples of mRNA from hummingbird embryos at different stages of development, transfer the samples to a nitrocellulose membrane, and then allow the mRNAs on the membrane to hybridize with a labeled probe recognizing beta-globin mRNA. If we expose a film to the membrane, the resulting image will look similar to the Southern blot in Figure 20.11, with one band of a given size showing up in each sample.

Question: What is required for Northern blotting?

Choices:
- A. a play on words
- B. gel electrophoresis

Prompt: Given the context, pick the right choice that answers the question


Question: Which event occurs first?

Choices:
- A. mRNAs on the membrane hybridize with a labeled probe
- B. gel electrophoresis

Prompt: Given the context, pick the right choice that answers the question


Question: What happens after the transfer of the samples to a nitrocellulose membrane?

Choices:
- A. gel electrophoresis
- B. one band showing up in each sample

Prompt: Given the context, pick the right choice that answers the question


Context: Analysis of hummingbird beta-globin gene expression with RT-PCR begins similarly to Northern blotting, with the isolation of mRNAs from different developmental stages of hummingbird embryos. Reverse transcriptase is added next to make cDNA, which then serves as a template for PCR amplification using primers from the beta-globin gene. When the products are run on a gel, copies of the amplified region will be observed as bands only in samples that originally contained the beta-globin mRNA.

Question: reverse transcriptase does what?

Choices:
- A. makes cDNA
- B. serves as a template

Prompt: Given the context, pick the right choice that answers the question


Question: What does cDNA do?

Choices:
- A. is added to reverse transcriptase
- B. serves as a template for PCR amplification

Prompt: Given the context, pick the right choice that answers the question


Question: What does the reverse transcriptase do?

Choices:
- A. serves as a template for PCR amplification
- B. isolates mRNAs

Prompt: Given the context, pick the right choice that answers the question


Context: Genome-wide expression studies are made possible by DNA microarray assays. A DNA microarray consists of tiny amounts of a large number of single-stranded DNA fragments representing different genes fixed to a glass slide in a tightly spaced array, or grid (see Figure 20.1). (The microarray is also called a DNA chip by analogy to a computer chip. ) Ideally, these fragments represent all the genes of an organism. Figure 20.15 outlines how the DNA fragments on a microarray are tested for hybridization with cDNA molecules that have been prepared from the mRNAs in particular cells of interest and labeled with fluorescent dyes.

Question: What is fixed to a glass slide?

Choices:
- A. a large number
- B. DNA fragments

Prompt: Given the context, pick the right choice that answers the question


Question: What is required to produce cDNA molecules?

Choices:
- A. mRNAs
- B. a microarray

Prompt: Given the context, pick the right choice that answers the question


Question: What is labeled with fluorescent dyes?

Choices:
- A. mRNAs
- B. cDNA molecules

Prompt: Given the context, pick the right choice that answers the question


Context: In one application of this approach, called in vitro mutagenesis, specific mutations are introduced into a cloned gene, and then the mutated gene is returned to a cell in such a way that it disables (knocks out) the normal cellular copies of the same gene. If the introduced mutations alter or destroy the function of the gene product, the phenotype of the mutant cell may help reveal the function of the missing normal protein.

Question: a cell disables the normal cellular copies of the same gene

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: Which event occurs first?

Choices:
- A. introduced mutations alter or destroy the function of the gene product
- B. specific mutations are introduced

Prompt: Given the context, pick the right choice that answers the question


Question: What happens if the mutations alter the function of the gene product?

Choices:
- A. the mutated gene is returned to a cell
- B. the function of the missing normal protein is revealed

Prompt: Given the context, pick the right choice that answers the question


Context: The successful cloning of whole plants from single differentiated cells was accomplished during the 1950s by F. C. Steward and his students at Cornell University, who worked with carrot plants (Figure 20.17). They found that differentiated cells taken from the root (the carrot) and incubated in culture medium could grow into normal adult plants, each genetically identical to the parent plant. These results showed that differentiation does not necessarily involve irreversible changes in the DNA. In plants, at least, mature cells can dedifferentiate and then give rise to all the specialized cell types of the organism.

Question: What was successfully cloned?

Choices:
- A. F.C. Steward
- B. carrot plants

Prompt: Given the context, pick the right choice that answers the question


Question: What was incubated in culture medium?

Choices:
- A. differentiated cells
- B. students at Cornell University

Prompt: Given the context, pick the right choice that answers the question


Question: What is the result of successful cloning?

Choices:
- A. irreversible changes in the DNA
- B. the cells grow into normal adult cells

Prompt: Given the context, pick the right choice that answers the question


Context: These researchers achieved the necessary dedifferentiation of donor nuclei by culturing mammary cells in nutrient-poor medium. They then fused these cells with enucleated sheep eggs. The resulting diploid cells divided to form early embryos, which were implanted into surrogate mothers. Out of several hundred implanted embryos, one successfully completed normal development, and Dolly was born.

Question: What is necessary for dedifferentiation of donor nuclei?

Choices:
- A. enucleated sheep eggs
- B. nutrient-poor medium

Prompt: Given the context, pick the right choice that answers the question


Question: What were implanted into surrogate mothers?

Choices:
- A. early embryos
- B. diploid cells

Prompt: Given the context, pick the right choice that answers the question


Question: What happened because of one successfully completed normal development?

Choices:
- A. several hundred implanted embryos
- B. Dolly was born

Prompt: Given the context, pick the right choice that answers the question


Context: Many early animal embryos contain stem cells capable of giving rise to differentiated embryonic cells of any type. Stem cells can be isolated from early embryos at a stage called the blastula stage or its human equivalent, the blastocyst stage (Figure 20.21). In culture, these embryonic stem (ES) cells reproduce indefinitely; and depending on culture conditions, they can be made to differentiate into a wide variety of specialized cells, including even eggs and sperm.

Question: What do ES cells produce?

Choices:
- A. culture conditions
- B. a wide variety of specialized cells

Prompt: Given the context, pick the right choice that answers the question


Question: Stem cells produce early embryos

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What can be eventually produced from stem cells isolated from early embryos?

Choices:
- A. a wide variety of specialized cells
- B. the blastula

Prompt: Given the context, pick the right choice that answers the question


Context: After the chromosomes duplicate in interphase, the diploid cell divides twice, yielding four haploid daughter cells.

Question: Haploid cells duplicate chromosomes during interphase

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. Chromosomes duplicate, then four haploid cells are produced, then the diploid cell divides twice
- B. Chromosomes duplicate, then the cell divides twice, then four haploid cells are produced

Prompt: Given the context, pick the right choice that answers the question


Context: Analysis of hummingbird beta-globin gene expression with RT-PCR begins similarly to Northern blotting, with the isolation of mRNAs from different developmental stages of hummingbird embryos. Reverse transcriptase is added next to make cDNA, which then serves as a template for PCR amplification using primers from the beta-globin gene.

Question: With what process does analysis of hummingbird beta-globin gene expression with RT-PCR begin?

Choices:
- A. Northern blotting
- B. Isolation of mRNAs

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without reverse transcriptase?

Choices:
- A. Primers from the beta-globin gene would not be produced
- B. cDNA would not be made

Prompt: Given the context, pick the right choice that answers the question


Question: Reverse transcriptase serves as a template for PCR amplification

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: Although adult animals have only tiny numbers of stem cells, scientists are learning to identify and isolate these cells from various tissues and, in some cases, to grow them in culture. With the right culture conditions (for instance, the addition of specific growth factors), cultured stem cells from adult animals have been made to differentiate into multiple types of specialized cells, although none are as versatile as ES cells.

Question: What grows in culture?

Choices:
- A. stem cells
- B. scientists

Prompt: Given the context, pick the right choice that answers the question


Question: What causes stem cells to differentiate into multiple types of specialized cells?

Choices:
- A. the right culture conditions
- B. adult animals

Prompt: Given the context, pick the right choice that answers the question


Question: Specific growth factors differentiate into multiple types of specialized cells

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: There are two major potential uses for human iPS cells. First, cells from patients suffering from diseases can be reprogrammed to become iPS cells, which can act as model cells for studying the disease and potential treatments. Human iPS cell lines have already been developed from individuals with type 1 diabetes, Parkinson's disease, and at least a dozen other diseases. Second, in the field of regenerative medicine, a patient's own cells could be reprogrammed into iPS cells and then used to replace nonfunctional tissues (Figure 20.22).

Question: What act as model cells for studying the disease and potential treatments?

Choices:
- A. patients suffering from diseases
- B. iPS cells

Prompt: Given the context, pick the right choice that answers the question


Question: What is necessary for replacement of nonfunctional tissues?

Choices:
- A. Parkinson's disease
- B. iPS cells

Prompt: Given the context, pick the right choice that answers the question


Question: What happens when the patient's own cells are reprogrammed?

Choices:
- A. Human iPS cell lines are developed
- B. replacement of nonfunctional tissues

Prompt: Given the context, pick the right choice that answers the question


Context: In a trial begun in France in 2000, ten young children with SCID were treated by the same procedure. Nine of these patients showed significant, definitive improvement after two years, the first indisputable success of gene therapy. However, three of the patients subsequently developed leukemia, a type of blood cell cancer, and one of them died. Two factors may have contributed to the development of leukemia: the insertion of the retroviral vector near a gene involved in the proliferation of blood cells and an unknown function of the replacement gene itself.

Question: What would happen without gene therapy?

Choices:
- A. leukemia would not have developed
- B. Ten young children would not have SCID

Prompt: Given the context, pick the right choice that answers the question


Question: The procedure caused leukemia in three of the patients

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Context: Genes conferring useful traits, such as pest resistance, herbicide resistance, delayed ripening, and increased nutritional value, can be transferred from one plant variety or species to another using the Ti plasmid as a vector. Technique Results Transformed cells carrying the transgene of interest can regenerate complete plants that exhibit the new trait conferred by the transgene. Genetic engineering is rapidly replacing traditional plant-breeding programs, especially for useful traits, such as herbicide or pest resistance, determined by one or a few genes. Crops engineered with a bacterial gene making the plants resistant to herbicides can grow while weeds are destroyed, and genetically engineered crops that can resist destructive insects reduce the need for chemical insecticides.

Question: What is required for complete plants to exhibit the new trait?

Choices:
- A. delayed ripening
- B. a vector

Prompt: Given the context, pick the right choice that answers the question


Question: What is destroyed?

Choices:
- A. weeds
- B. genetically engineered crops

Prompt: Given the context, pick the right choice that answers the question


Question: What can genetically engineered crops resist?

Choices:
- A. chemical insecticides
- B. destructive insects

Prompt: Given the context, pick the right choice that answers the question


Context: After we've identified the location of a clone carrying the beta-globin gene, we can grow some cells from that colony in liquid culture in a large tank and then easily isolate many copies of the gene for our studies.

Question: What is the final product of growing cells in liquid culture?

Choices:
- A. many copies of the gene
- B. a clone carrying the beta-globin gene

Prompt: Given the context, pick the right choice that answers the question


Question: What is produced by growing cells in a liquid culture?

Choices:
- A. many copies of the gene
- B. the beta-globulin gene

Prompt: Given the context, pick the right choice that answers the question


Context: Advocates of a cautious approach toward GM crops fear that transgenic plants might pass their new genes to close relatives in nearby wild areas. We know that lawn and crop grasses, for example, commonly exchange genes with wild relatives via pollen transfer. If crop plants carrying genes for resistance to herbicides, diseases, or insect pests pollinated wild ones, the offspring might become super weeds that are very difficult to control.

Question: transgenic crops might do what?

Choices:
- A. fear
- B. pass their new genes to close relatives

Prompt: Given the context, pick the right choice that answers the question


Question: What can be produced if crop plants carrying genes for resistance pollinated wild ones?

Choices:
- A. super weeds
- B. insect pests

Prompt: Given the context, pick the right choice that answers the question


Context: In this method, we carry out gel electrophoresis on samples of mRNA from hummingbird embryos at different stages of development, transfer the samples to a nitrocellulose membrane, and then allow the mRNAs on the membrane to hybridize with a labeled probe recognizing beta-globin mRNA.

Question: What is the correct order of events?

Choices:
- A. Gel electrophoresis, then transfer of samples to nitrocellulose membrane, then mRNAs hybridize to a labeled probe
- B. Gel electrophoresis, then embryo development, then transfer of samples to a nitrocellulose membrane.

Prompt: Given the context, pick the right choice that answers the question


Context: After the current is turned off, a DNA-binding dye (ethidium bromide) is added. This dye fluoresces pink in ultraviolet light, revealing the separated bands to which it binds.

Question: What would happen without the dye?

Choices:
- A. Current would not be turned off
- B. separated bands would not be revealed

Prompt: Given the context, pick the right choice that answers the question


Question: Ethidium bromide binds DNA.

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: For example, a transgene for a human blood protein such as antithrombin can be inserted into the genome of a goat in such a way that the transgene's product is secreted in the animal's milk (Figure 20.24). The protein is then purified from the milk (which is easier than purification from a cell culture).

Question: Antithrombin can be purified the animal's milk

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following produces antithrombin?

Choices:
- A. The genome of a goat
- B. the transgene

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without the transgene?

Choices:
- A. the protein could not be purified from the milk
- B. the protein could not be purified from a cell culture

Prompt: Given the context, pick the right choice that answers the question


Context: After such long fragments were put in order, each fragment was cut into smaller pieces, which were cloned in plasmids or phages, ordered in turn, and finally sequenced.

Question: long fragments are cloned into plasmids or phages

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. long fragments are put in order, then each fragment is cut, then the smaller pieces are cloned into plasmids are phages
- B. long fragments are put in order, then each fragment is cut, then plasmids or phages are sequenced

Prompt: Given the context, pick the right choice that answers the question


Context: Messenger RNA, the carrier of information from DNA to the cell's protein-synthesizing machinery, is transcribed from the template strand of a gene. An enzyme called an RNA polymerase pries the two strands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand, thus elongating the RNA polynucleotide (Figure 17.7).

Question: What does messenger RNA do?

Choices:
- A. carries information from DNA
- B. synthesizes protein

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following is transcribed from the template strand of a gene?

Choices:
- A. Messenger RNA
- B. the cell's protein-synthesizing machinery

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if RNA polymeraste did not join together RNA nucleotides?

Choices:
- A. the RNA polynucleotide would not be elongated
- B. RNA polymerase would not pry the two strands of DNA apart

Prompt: Given the context, pick the right choice that answers the question


Question: The cell's protein-synthesizing machinery is required to produce RNA

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following is required to elongate the RNA polynucleotide?

Choices:
- A. the cell's protein-synthesizing machinery
- B. DNA

Prompt: Given the context, pick the right choice that answers the question


Context: As RNA polymerase moves along the DNA, it continues to untwist the double helix, exposing about 10-20 DNA nucleotides at a time for pairing with RNA nucleotides (Figure 17.9). The enzyme adds nucleotides to the 3' end of the growing RNA molecule as it continues along the double helix. In the wake of this advancing wave of RNA synthesis, the new RNA molecule peels away from its DNA template, and the DNA double helix re-forms.

Question: what would happen if 10-20 DNA nucleotides were not exposed?

Choices:
- A. RNA polymerase would not untwist the double helix
- B. Nucleotides would not be paired with RNA nucleotides

Prompt: Given the context, pick the right choice that answers the question


Question: RNA polymerase untwists the double helix

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What happens when the new RNA molecule peels away from its DNA template?

Choices:
- A. The DNA double helix re-forms
- B. RNA synthesis

Prompt: Given the context, pick the right choice that answers the question


Context: When cAMP binds to this regulatory protein, CAP assumes its active shape and can attach to a specific site at the upstream end of the lac promoter (Figure 18.5a). This attachment increases the affinity of RNA polymerase for the promoter, which is actually rather low even when no repressor is bound to the operator.

Question: What would happen without CAP?

Choices:
- A. affinity of RNA polymerase for the promoter would not increase
- B. No repressor would bind to the operator

Prompt: Given the context, pick the right choice that answers the question


Question: What does cAMP do?

Choices:
- A. Assumes its active shape
- B. binds to a regulatory protein

Prompt: Given the context, pick the right choice that answers the question


Question: What happens when the CAP attaches to a specific site at the upstream end of the lac promoter?

Choices:
- A. no repressor is bound to the operator
- B. increase in the affinity of RNA polymerase for the promoter

Prompt: Given the context, pick the right choice that answers the question


Context: To mark a particular protein for destruction, the cell commonly attaches molecules of a small protein called ubiquitin to the protein. Giant protein complexes called proteasomes then recognize the ubiquitin-tagged proteins and degrade them (Figure 18.14).

Question: Small proteins are attached to ubiquitin

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without ubiquitin?

Choices:
- A. proteins would not be marked for destruction
- B. proteasomes would not be degraded

Prompt: Given the context, pick the right choice that answers the question


Context: Crossing over begins very early in prophase I as homologous chromosomes pair loosely along their lengths. Each gene on one homolog is aligned precisely with the corresponding gene on the other homolog. In a single crossover event, the DNA of two nonsister chromatids: one maternal and one paternal chromatid of a homologous pair: is broken by specific proteins at precisely corresponding points, and the two segments beyond the crossover point are each joined to the other chromatid. Thus, a paternal chromatid is joined to a piece of maternal chromatid beyond the crossover point, and vice versa. In this way, crossing over produces chromosomes with new combinations of maternal and paternal alleles (see Figure 13.11).

Question: Which entities are responsible for breaking DNA?

Choices:
- A. homologous pairs
- B. proteins

Prompt: Given the context, pick the right choice that answers the question


Question: What is the correct order of events?

Choices:
- A. homologous chromosomes pair, then DNA is broken, and then two segments are joined
- B. homologous chromosomes pair, then new combinations of maternal and paternal alleles are produced, then DNA is broken

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without the specific proteins?

Choices:
- A. Homologous chromosomes would not pair
- B. new combinations of maternal and paternal alleles would not be produced

Prompt: Given the context, pick the right choice that answers the question


Question: Which of the following events occur at the same time?

Choices:
- A. crossing over and homologs align
- B. DNA of nonsister chromatids is broken and two segments beyond the crossover point are each joined to the other chromatid

Prompt: Given the context, pick the right choice that answers the question


Context: The red blood cells of people with sickle-cell disease become distorted in shape, or sickled, under low-oxygen conditions (see Figure 5.21), as occurs in the capillaries. These sickled cells can clump together and block the flow of blood in the capillaries, resulting in serious damage to organs such as the kidney, heart, and brain.

Question: What causes red blood cells to become distorted in shape?

Choices:
- A. flow of blood in the capillaries
- B. low-oxygen conditions

Prompt: Given the context, pick the right choice that answers the question


Question: Distorted red blood cells clump together and block the flow of blood in the capillaries, resulting in serious damage to organs

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What is caused by sickled cells clumping together?

Choices:
- A. serious damage to organs
- B. low oxygen conditions

Prompt: Given the context, pick the right choice that answers the question


Context: Retrotransposons always leave a copy at the original site during transposition, since they are initially transcribed into an RNA intermediate (Figure 21.10). To insert at another site, the RNA intermediate is first converted back to DNA by reverse transcriptase, an enzyme encoded by the retrotransposon. (Reverse transcriptase is also encoded by retroviruses, as you learned in Chapter 19. In fact, retroviruses may have evolved from retrotransposons.) Another cellular enzyme catalyzes insertion of the reverse-transcribed DNA at a new site.

Question: The retrotransposon encodes reverse transcriptase

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without the RNA intermediate?

Choices:
- A. the retrotransposon could not insert at another site
- B. retroviruses would not encode reverse transcriptase

Prompt: Given the context, pick the right choice that answers the question


Question: What does reverse transcriptase do?

Choices:
- A. converts the RNA intermediate back to DNA
- B. encodes retroviruses

Prompt: Given the context, pick the right choice that answers the question


Context: These rRNA molecules are transcribed from a single transcription unit that is repeated tandemly hundreds to thousands of times in one or several clusters in the genome of a multicellular eukaryote. The many copies of this rRNA transcription unit help cells to quickly make the millions of ribosomes needed for active protein synthesis. The primary transcript is cleaved to yield the three rRNA molecules, which combine with proteins and one other kind of rRNA (5S rRNA) to form ribosomal subunits.

Question: What would happen if the primary transcript was not cleaved?

Choices:
- A. ribosomal subunits would not be formed
- B. rRNA molecules would not be transcribed from a single transcription unit

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen without millions of ribosomes?

Choices:
- A. active protein synthesis would not occur
- B. the primary transcript would not be cleaved

Prompt: Given the context, pick the right choice that answers the question


Question: what is the correct order of events?

Choices:
- A. rRNA molecules are transcribed, then the primary transcript is cleaved, then ribosomal subunits are formed
- B. rRNA molecules are transcribed, then active protein synthesis occurs, then the primary transcript is cleaved

Prompt: Given the context, pick the right choice that answers the question


Question: What is eventually produced when the primary transcript is cleaved?

Choices:
- A. active proteins
- B. ribosomal subunits

Prompt: Given the context, pick the right choice that answers the question


Context: In allopatric speciation (from the Greek allos, other, and patra, homeland), gene flow is interrupted when a population is divided into geographically isolated subpopulations.

Question: Gene flow interruption causes populations to be divided into geographically isolated subpopulations

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if a population is not divided into geographically isolated subpopulations?

Choices:
- A. Allopatric speciation would not occur
- B. gene flow would not occur

Prompt: Given the context, pick the right choice that answers the question


Context: Once geographic separation has occurred, the separated gene pools may diverge. Different mutations arise, and natural selection and genetic drift may alter allele frequencies in different ways in the separated populations. Reproductive isolation may then arise as a by-product of selection or drift having caused the populations to diverge genetically.

Question: Which of the following events can occur at the same time?

Choices:
- A. different mutations arise and natural selection and genetic drift alter allele frequencies
- B. geographic separation and gene pools diverge

Prompt: Given the context, pick the right choice that answers the question


Question: What can separated gene pools produce?

Choices:
- A. geographic separation
- B. reproductive isolation

Prompt: Given the context, pick the right choice that answers the question


Question: Geographic separation may cause reproductive isolation

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: Though rarer than allopatric speciation, sympatric speciation can occur when gene flow to and from the isolated subpopulation is blocked.

Question: Allopatric speciation occurs when gene flow to and from the isolated population is blocked

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Context: The RNA molecule whose sequence is best suited to the surrounding environment and has the greatest ability to replicate itself will leave the most descendant molecules. Occasionally, a copying error will result in a molecule that folds into a shape that is even more stable or more adept at self-replication than the ancestral sequence.

Question: Copying errors can result in leaving the most descendant molecules

Choices:
- A. False
- B. True

Prompt: Given the context, pick the right choice that answers the question


Question: What do copying errors produce?

Choices:
- A. the ancestral sequence
- B. a molecule that folds into a shape that is even more stable or more adept at self-replication

Prompt: Given the context, pick the right choice that answers the question


Context: When the organism dies, it stops accumulating carbon, and the amount of carbon-12 in its tissues does not change over time. However, the carbon-14 that it contains at the time of death slowly decays into another element, nitrogen-14.

Question: Carbon-12 slowly decays into nitrogen-14.

Choices:
- A. True
- B. False

Prompt: Given the context, pick the right choice that answers the question


Question: What happens when an organism dies?

Choices:
- A. the time of death slowly decays into another element
- B. the amount of carbon-12 in its tissues does not change over time

Prompt: Given the context, pick the right choice that answers the question


Context: These chloride transport channels are defective or absent in the plasma membranes of children who inherit two recessive alleles for cystic fibrosis. The result is an abnormally high concentration of extracellular chloride, which causes the mucus that coats certain cells to become thicker and stickier than normal. The mucus builds up in the pancreas, lungs, digestive tract, and other organs, leading to multiple (pleiotropic) effects, including poor absorption of nutrients from the intestines, chronic bronchitis, and recurrent bacterial infections.

Question: What causes an abnormally high concentration of extracellular chloride?

Choices:
- A. Defective or absent chloride transport channels
- B. mucus that coats certain cells becomes thicker and stickier than normal

Prompt: Given the context, pick the right choice that answers the question


Question: What would happen if the concentration of extracellular chloride did not become abnormally high?

Choices:
- A. Chronic bronchitis would not occur
- B. children would not inherit two recessive alleles

Prompt: Given the context, pick the right choice that answers the question


Question: Which entity directly causes poor absorption of nutrients?

Choices:
- A. Mucus
- B. the pancreas

Prompt: Given the context, pick the right choice that answers the question