Question 1

Every HIV particle contains two RNA molecules. If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true?

Accepted Answer

A) There are now fewer genes within the viral particle. 
B) There are now more genes within the viral particle. 
C) A point substitution mutation has occurred in the retroviral genome. 
D) The retroviral equivalent of crossing over has occurred, no doubt resulting in a heightened positive effect. 
E) One of the RNA molecules has experienced gene duplication as the result of translocation.

Question 2

Use the following information to answer the questions below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All ten of the original colonists had free earlobes, and two were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
-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

Accepted Answer

A) diploidy. 
B) gene flow. 
C) genetic drift. 
D) disruptive selection. 
E) stabilizing selection.

Question 3

The three main mechanisms that alter allele frequencies and change the genetic composition of populations are

Accepted Answer

A) natural selection, bottleneck effect, and founder effect. 
B) natural selection, gene flow, and random mating. 
C) natural selection, genetic drift, and gene flow. 
D) natural selection, random mating, and gene flow. 
E) natural selection, gene flow, and large population size.

Question 4

Use this information below to answer the following questions.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
-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?

Accepted Answer

A) The population is undergoing genetic drift. 
B) The two phenotypes are about equally adaptive under laboratory conditions. 
C) The genotype AA is lethal. 
D) There has been a high rate of mutation of allele A to allele a. 
E) There has been sexual selection favouring allele a.

Question 5

Use the following information to answer the questions below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
-What should be the proportion of heterozygous individuals in populations that live here?

Accepted Answer

A) 0.04 
B) 0.16 
C) 0.20 
D) 0.32 
E) 0.80

Question 6

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome from an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogues (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.
-Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?

Accepted Answer

A) using a series of NAs, one at a time, and changed about once a week 
B) using a single PI, but slowly increasing the dosage over the course of a week 
C) using high doses of NA and a PI at the same time for a period not to exceed one day 
D) using moderate doses of NA and two different PIs at the same time for several months

Question 7

Use the following figure to answer the questions below.
In a very large population, a quantitative trait has the following distribution pattern:
 
-What is true of the trait whose frequency distribution in a large population appears in the previous figure? It has probably undergone

Accepted Answer

A) directional selection. 
B) stabilizing selection. 
C) disruptive selection. 
D) normal selection.

Question 8

You sample a population of butterflies and find that 56% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population?

Accepted Answer

A) 0.07 
B) 0.08 
C) 0.09 
D) 0.70 
E) Allele frequency cannot be determined from this information.

Question 9

Most invertebrates have a cluster of ten similar Hox genes, all located on the same chromosome. Most vertebrates have four such clusters of Hox genes, located on four nonhomologous chromosomes. The process that could have potentially contributed to the cluster's presence on more than one chromosome was

Accepted Answer

A) binary fission. 
B) translation. 
C) gene duplication. 
D) nondisjunction. 
E) transcription.

Question 10

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?

Accepted Answer

A) gene variability = 0%; number of alleles = 0 
B) gene variability = 0%; number of alleles = 1 
C) gene variability = 0%; number of alleles = 2 
D) gene variability > 0%; number of alleles = 2 
E) Without more information, gene variability and number of alleles cannot be determined.

Question 11

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

Accepted Answer

A) sexual selection. 
B) disruptive selection. 
C) balancing selection. 
D) stabilizing selection. 
E) frequency-dependent selection.

Question 12

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. The actual forelimbs of these mammals do not seem to be optimally arranged because

Accepted Answer

A) natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time. 
B) in many cases, phenotype is not merely determined by genotype, but by the environment as well. 
C) though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design. 
D) natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

Question 13

If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of

Accepted Answer

A) genetic drift. 
B) bottleneck effect. 
C) founder effect. 
D) all three of these. 
E) both the first and third of these.

Question 14

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?

Accepted Answer

A) Advantageous alleles do not arise on demand. 
B) A population's evolution is limited by historical constraints. 
C) Adaptations are often compromises. 
D) Evolution can be influenced by environmental change.

Question 15

In Kluane National Park, red squirrels have been recorded giving birth 18 days earlier than a decade ago. Offspring born earlier become larger and more likely to survive. What mode of selection best describes these current research findings?

Accepted Answer

A) stabilizing selection 
B) directional selection 
C) disruptive selection 
D) transitional selection 
E) Selection will vary depending on temperature and amount of snow in spring.

Question 16

The higher the proportion of loci that are "fixed" in a population, the lower is that population's

Accepted Answer

A) nucleotide variability only. 
B) genetic polyploidy only. 
C) average heterozygosity only. 
D) nucleotide variability, average heterozygosity, and genetic polyploidy. 
E) nucleotide variability and average heterozygosity only.

Question 17

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?

Accepted Answer

A) heterozygote advantage 
B) stabilizing selection 
C) diploidy 
D) balancing selection

Question 18

Use this information below to answer the following questions.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
-What is the estimated frequency of allele A in the gene pool?

Accepted Answer

A) 0.25 
B) 0.50 
C) 0.75

Question 19

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?

Accepted Answer

A) 0.7 
B) 0.49 
C) 0.21 
D) 0.42 
E) 0.09

Question 20

The volcano is currently dormant, but in a hypothetical future scenario, satellite cones at the base of Mt. Kilimanjaro spew sulphurous gases and lava, destroying all life located between the base and 1830 metres above sea level. As a result of this catastrophe, how should the frequency of the sickle-cell allele change in the remnant human population that survives above 1830 metres, and which phenomenon accounts for this change in allele frequency?

Accepted Answer

A) decreases; disruptive selection 
B) increases; genetic drift 
C) decreases; gene flow 
D) increases; nonrandom mating 
E) decreases; bottleneck effect

Exam 23: The Evolution of Populations