Biology 20, 22, 23

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In recombinant DNA methods, the term vector can refer to

a plasmid used to transfer DNA into a living cell.

DNA technology has many medical applications. Which of the following is not done routinely at present?

introduction of genetically engineered genes into human gametes

Expression of a cloned eukaryotic gene in a bacterial cell involves many challenges. The use of mRNA and reverse transcriptase is part of a strategy to solve the problem of

post-transcriptional processing.

A paleontologist has recovered a bit of tissue from the 400-year-old preserved skin of an extinct dodo (a bird). The researcher would like to compare a specific region of the DNA from the sample with DNA from living birds. Which of the following would be most useful for increasing the amount of dodo DNA available for testing?

polymerase chain reaction (PCR)

Plants are more readily manipulated by genetic engineering than are animals because

a somatic plant cell can often give rise to a complete plant.

Which of the following would not be true of cDNA produced using human brain tissue as the starting material?

It could be used to create a complete genomic library.

Which of the following tools of recombinant DNA technology is incorrectly paired with its use?

DNA ligase-enzyme that cuts DNA, creating the sticky ends of restriction fragments

As genetic technology makes testing for a wide variety of genotypes possible, which of the following is likely to be an increasingly troublesome issue?

the need to legislate for the protection of the privacy of genetic information

One possible use of transgenic plants is in the production of human proteins, such as vaccines. Which of the following is a possible hindrance that must be overcome?

prevention of transmission of plant allergens to the vaccine recipients

Why would Gleevec most probably cause remission of the disease?

The drug inhibits the specific thymine kinase receptor.

Which of the following would be a reasonably efficient technique for confirming the diagnosis of CML?

FISH study to determine the chromosomal location of all chromosome 22 q fragments

Which of the following is one of the technical reasons why gene therapy is problematic?

Transferred genes may not have appropriately controlled activity.

One successful form of gene therapy has involved delivery of an allele for the enzyme adenosine deaminase (ADA) to bone marrow cells of a child with SCID, and delivery of these engineered cells back to the bone marrow of the affected child. What is one major reason for the success of this procedure as opposed to many other efforts at gene therapy?

The engineered cells, when reintroduced into the patient, find their way back to the bone marrow.

Scientists developed a set of guidelines to address the safety of DNA technology. Which of the following is one of the adopted safety measures?

Microorganisms used in recombinant DNA experiments are genetically crippled to ensure that they cannot survive outside of the laboratory.

Genetically engineered plants

include a transgenic rice plant that can help prevent vitamin A deficiency.

Genetic engineering is being used by the pharmaceutical industry. Which of the following is not currently one of the uses?

creation of products that will remove poisons from the human body

Gene therapy

had apparent success in treating disorders involving bone marrow cells.

A researcher is using adult stem cells and comparing them to other adult cells from the same tissue. Which of the following is a likely finding?

The cells from the two sources exhibit different patterns of DNA methylation.

Which of the following is true of embryonic stem cells but not of adult stem cells?

They make up the majority of cells of the tissue from which they are derived.

Reproductive cloning of human embryos is generally considered unethical. However, on the subject of therapeutic cloning there is a wider divergence of opinion. Which of the following is a likely explanation?

Cloning to produce embryonic stem cells may lead to great medical benefits for many.

Which of the following problems with animal cloning might result in premature death of the clones?

abnormal regulation due to variant methylation

In 1997, Dolly the sheep was cloned. Which of the following processes was used?

fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate

Which of the following is most closely identical to the formation of twins?

organismal cloning

Which of the following techniques used to analyze gene function depends on the specificity of DNA base complementarity?

in vitro mutagenesis

A researcher has used in vitro mutagenesis to mutate a cloned gene and then has reinserted this into a cell. In order to have the mutated sequence disable the function of the gene, what must then occur?

recombination resulting in replacement of the wild type with the mutated gene

RNAi methodology uses double-stranded pieces of RNA to trigger a breakdown or blocking of mRNA. For which of the following might it more possibly be useful?

to decrease the production from a harmful gain-of-function mutated gene

Which uses reverse transcriptase to make cDNA followed by amplification?


Which describes the transfer of polypeptide sequences to a membrane to analyze gene expression?

Western blotting

Which was developed by a British researcher and causes DNA sequences to be transferred to a membrane and identified with a probe?

Southern blotting

DNA microarrays have made a huge impact on genomic studies because they

allow the expression of many or even all of the genes in the genome to be compared at once.

Dideoxyribonucleotide chain-termination is a method of

sequencing DNA.

Which of the following procedures would produce RFLPs?

incubating DNA with restriction enzymes

RFLP analysis can be used to distinguish between alleles based on differences in which of the following?

restriction enzyme recognition sites between the alleles

DNA fragments from a gel are transferred to a nitrocellulose paper during the procedure called Southern blotting. What is the purpose of transferring the DNA from a gel to a nitrocellulose paper?

to attach the DNA fragments to a permanent substrate

Which of the following modifications is least likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?

altering the nucleotide sequence of the DNA fragment

In order to identify a specific restriction fragment using a probe, what must be done?

A, B, and C are correct.

Restriction fragments of DNA are typically separated from one another by which process?

gel electrophoresis

Which of the following separates molecules by movement due to size and electrical charge?

gel electrophoresis

Which of the following cuts DNA molecules at specific locations?

restriction enzymes

Which of the following is used to make complementary DNA (cDNA) from RNA?

reverse transcriptase

Which of the following seals the sticky ends of restriction fragments to make recombinant DNA?

DNA ligase

Which of the following produces multiple identical copies of a gene for basic research or for large-scale production of a gene product?

gene cloning

The major advantage of using artificial chromosomes such as YACs and BACs for cloning genes is

YACs and BACs can carry much larger DNA fragments than ordinary plasmids can.

To introduce a particular piece of DNA into an animal cell, such as that of a mouse, you would find more probable success with which of the following methods?

electroporation followed by recombination

4. DNA polymerase extends the primers to make a copy of the target DNA.

2, 1, 4

Yeast artificial chromosomes contain which of the following elements?

centromere, telomeres, and an origin of replication

How does a genomic library differ from a cDNA library?

A genomic library can be made using a restriction enzyme and DNA ligase only, whereas a cDNA library requires both of these as well as reverse transcriptase and DNA polymerase.

The DNA fragments making up a genomic library are generally contained in

recombinant plasmids of bacteria.

Why are yeast cells frequently used as hosts for cloning?

they are eukaryotic cells

A gene that contains introns can be made shorter (but remain functional) for genetic engineering purposes by using

reverse transcriptase to reconstruct the gene from its mRNA.

A principal problem with inserting an unmodified mammalian gene into a bacterial plasmid, and then getting that gene expressed in bacteria, is that

bacteria cannot remove eukaryotic introns.

Bacteria that do not take up any plasmids would grow on which media?

the nutrient broth only

Bacteria containing a plasmid into which the eukaryotic gene has integrated would grow in

the ampicillin broth and the nutrient broth.

Bacteria that contain the plasmid, but not the eukaryotic gene, would grow

in all four types of broth.

Bacteria containing recombinant plasmids are often identified by which process?

exposing the bacteria to an antibiotic that kills cells lacking the resistant plasmid

V. Use ligase to seal plasmid DNA to nonplasmid DNA.


How does a bacterial cell protect its own DNA from restriction enzymes?

adding methyl groups to adenines and cytosines

What is the enzymatic function of restriction enzymes?

to cleave nucleic acids at specific sites

Assume that you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzyme X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y, but not for X. Your strategy should be to

cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with the same enzyme.

Which of the following pairs of structures is least likely to represent homology?

The wings of a bird and those of an insect

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that

humans and chimpanzees share a relatively recent common ancestor.

Within a few weeks of treatment with the drug 3TC, a patient's HIV population consists entirely of 3TC-resistant viruses. How can this result best be explained?

A few drug-resistant viruses were present at the start of treatment, and natural selection increased their frequency

Which of the following observations helped Darwin shape his concept of descent with modification?

South American temperate plants are more similar to the tropical plants of South America than to the temperate plants of Europe.

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data?

Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

Which of the following is not an observation or inference on which natural selection is based?

Poorly adapted individuals never produce offspring.

The theory of evolution is most accurately described as

an overarching explanation, supported by much evidence, for how populations change over time.

Monkeys of South and Central America have prehensile tails, meaning that their tails can be used to grasp objects. The tails of African and Asian monkeys are not prehensile. Which discipline is most likely to provide an evolutionary explanation for how this difference in tails came about?


It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that

island forms and mainland forms descended from common ancestors.

Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would best help distinguish between an explanation based on homology versus one based on convergent evolution?

The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.

Which of the following statements most detracts from the claim that the human appendix is a completely vestigial organ?

The appendix has a substantial amount of defensive lymphatic tissue.

Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree?

Relationships between DNA sequences among the species did not match relationships between skeletal patterns.

Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?

All organisms use essentially the same genetic code.

Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?

Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.

If two modern organisms are distantly related in an evolutionary sense, then one should expect that

they should share fewer homologous structures than two more closely related organisms.

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

None of the individual insects should have possessed genomes that made them resistant to DDT

Which statement best describes the evolution of pesticide resistance in a population of insects?

Offspring of insects that are genetically resistant to the pesticide become more abundant as the susceptible insects die off.

In a hypothetical environment, fishes called pike-cichlids are visual predators of algae-eating fish (i.e., they locate their prey by sight). If a population of algae-eaters experiences predation pressure from pike-cichlids, which of the following should least likely be observed in the algae-eater population over the course of many generations?

Selection for larger female algae-eaters, bearing broods composed of more, and larger, young

Evolutionary trees such as this are properly understood by scientists to be


Which pair would probably have agreed with the process that is depicted by this tree?

Lamarck and Wallace

Which of Darwin's ideas had the strongest connection to Darwin having read Malthus's essay on human population growth?

Struggle for existence

Which of the following must exist in a population before natural selection can act upon that population?

Genetic variation among individuals

Which of the following statements is an inference of natural selection?

Subsequent generations of a population should have greater proportions of individuals that possess traits better suited for success in unchanging environments.

During drought years on the Galapagos, small, easily eaten seeds become rare, leaving mostly large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should one expect to result from natural selection?

More small-beaked birds dying than larger-beaked birds. The offspring produced in subsequent generations have a higher percentage of birds with large beaks.

If the HMS Beagle had completely bypassed the Galapagos Islands, Darwin would have had a much poorer understanding of the

ability of populations to undergo modification as they adapt to a particular environment.

4. Poorly adapted individuals have decreased survivorship.

2 → 4 → 1 → 3

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?

Well-adapted individuals leave more offspring, and thus contribute more to the next generation's gene pool, than do poorly adapted individuals.

Natural selection is based on all of the following except

individuals adapt to their environments and, thereby, evolve. Which of these conditions should completely prevent the occurrence of natural selection in a population over time?: All variation between individuals is due only to environmental factors.

In Darwin's thinking, the more closely related two different organisms are, the

more recently they shared a common ancestor. Charles Darwin was the first person to propose: a mechanism for evolution that was supported by evidence.

Which of these naturalists synthesized a concept of natural selection independently of Darwin?

Alfred Wallace

As a young biologist, Charles Darwin had expected the living plants of temperate South America would resemble those of temperate Europe, but he was surprised to find that they more closely resembled the plants of tropical South America. The biological explanation for this observation is most properly associated with the field of


Darwin's mechanism of natural selection required long time spans in order to modify species. From whom did Darwin get the concept of Earth's ancient age?

Charles Lyell

Which pair would have been likely to agree that strata such as those depicted here were deposited gradually over long periods of time by subtle mechanisms that are still at work?

Hutton and Lyell

Who would have proposed that the boundaries between each stratum mark the occurrence of different localized floods?


In the mid-1900s, the Soviet geneticist Lysenko believed that his winter wheat plants, exposed to ever-colder temperatures, would eventually give rise to ever more cold-tolerant winter wheat. Lysenko's attempts in this regard were most in agreement with the ideas of


During a study session about evolution, one of your fellow students remarks, "The giraffe stretched its neck while reaching for higher leaves; its offspring inherited longer necks as a result." Which statement is most likely to be helpful in correcting this student's misconception?

Characteristics acquired during an organism's life are generally not passed on through genes.

What was the prevailing notion prior to the time of Lyell and Darwin?

Earth is a few thousand years old, and populations are unchanging.

Which of the events described below agrees with the idea of catastrophism?

The sudden demise of the dinosaurs, and various other groups, by the impact of a large extraterrestrial body with Earth

Catastrophism, meaning the regular occurrence of geological or meteorological disturbances (catastrophes), was Cuvier's attempt to explain the existence of

the fossil record.

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating

stabilizing selection.

No two people are genetically identical, except for identical twins. The chief cause of genetic variation among human individuals is

the reshuffling of alleles in sexual reproduction.

Natural selection changes allele frequencies in populations because some __________ survive and reproduce more successfully than others.


There are 40 individuals in population 1, all of which have genotype A1A1, and there are 25 individuals in population 2, all of genotype A2A2. Assume that these populations are located far from one another and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is mostly likely an example of

genetic drift.

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?


There are those who claim that the theory of evolution cannot be true because the apes, which are supposed to be closely related to humans, do not likewise share the same large brains, capacity for complicated speech, and tool-making capability. They reason that if these features are generally beneficial, then the apes should have evolved them as well. Which of these provides the best argument against this misconception?

Advantageous alleles do not arise on demand.

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these mammals do not seem to be optimally arranged is because

natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

The same gene that causes various coat patterns in wild and domesticated cats also causes the cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations?

Phenotype is often the result of compromise.

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of

frequency-dependent selection.

Male satin bowerbirds adorn structures that they build, called "bowers," with parrot feathers, flowers, and other bizarre ornaments in order to attract females. Females inspect the bowers and, if suitably impressed, allow males to mate with them. The evolution of this male behavior is due to

sexual selection.

5. disruptive selection

directional selection and adaptation

What is true of the trait whose frequency distribution in a large population appears above? It has probably undergone

stabilizing selection.

Heterozygote advantage should be most closely linked to which of the following?

stabilizing selection

Mules are relatively long-lived and hardy organisms that cannot, generally speaking, perform successful meiosis. Consequently, which statement about mules is true?

They have a relative evolutionary fitness of zero.

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet lacks the amino acid, phenylalanine. What maintains the presence of this harmful allele in a population's gene pool?


A certain species of land snail exists as either a cream color or a solid brown color. Intermediate individuals are relatively rare. Which of the following terms best describes this?

disruptive selection

The average birth weight for human babies is about 3 kg. Which of the following terms best describes this?

stabilizing selection

Fossil evidence indicates that horses have gradually increased in size over geologic time. Which of the following terms best describes this?

directional selection

Most Swiss starlings produce four to five eggs in each clutch. Those producing fewer or more than this have reduced fitness. Which of the following terms best describes this?

stabilizing selection

Which describes brightly colored peacocks mating more frequently than drab peacocks?

sexual selection

Which describes an African butterfly species that exists in two strikingly different color patterns?

disruptive selection

If neutral variation is truly "neutral," then it should have no effect on

relative fitness.

Which of the following statements best summarizes evolution as it is viewed today?

It is the differential survival and reproduction of the most-fit phenotypes.

When we say that an individual organism has a greater fitness than another individual, we specifically mean that the organism

leaves more viable offspring than others of its species.

The Darwinian fitness of an individual is measured most directly by

the number of its offspring that survive to reproduce.

If one excludes the involvement of gender in the situation described in the paragraph above, then the pattern that is apparent in the fossil record is most similar to one that should be expected from

disruptive selection.

Which addition to the information in the paragraph above would make more than one of the answers listed in the previous question correct?

If females killed female offspring whose voices were too deep.

If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females, and increasing larynx size in adult males, then

sexual dimorphism was developing over time in these species.

Sexual dimorphism is most often a result of

intersexual selection.

5. Sexual selection

4, 2, 1, 5, 3

Over the course of evolutionary time, what should occur?

Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.

The outcome of the conflict between bacteria and bacteriophage at any point in time results from

frequency-dependent selection.

Natural selection is most nearly the same as

differential reproductive success.

Gene flow is a concept best used to describe an exchange between


Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing

gene flow.

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to

cross your flies with flies from another lab.

In which population would it be least likely that an accident would significantly alter the frequency of the brown allele?

Population B.

If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of

genetic drift.

If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planet's population reaches 10,000?


Which of these is closest to the allele frequency in the founding population?

0.1 a, 0.9 A

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?


If there are 4,000 children born to this generation, how many would be expected to have AB blood under the conditions of Hardy-Weinberg equilibrium?


What is the frequency of the B allele?


You sample a population of butterflies and find that 42% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population?

Allele frequency cannot be determined from this information.

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals with Aa genotype?


In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the percentage of the population that is heterozygous for this allele?


In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.4. What is the percentage of the population that is homozygous for this allele?


What proportion of the population is probably heterozygous (Aa) for this trait?


What is the estimated frequency of allele A in the gene pool?


What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?

The two phenotypes are about equally adaptive under laboratory conditions.

Which is a true statement concerning genetic variation?

It must be present in a population before natural selection can act upon the population.

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