Q: In a population, the allele frequencies for a gene with three alleles are $$p = 0.5$$, $$q = 0.3$$, and $$r = 0.2. $$What is the expected frequency of the heterozygote genotype $$pq$$ under Hardy-Weinberg equilibrium?

$$2pq = 2 \times 0.5 \times 0.3 = 0.3$$

Question 1

Which of the following is the only process that creates new alleles in a gene pool?

Accepted Answer

Mutation

Question 2

A population of 100 pea plants is in Hardy-Weinberg equilibrium for a gene with two alleles (AA = smooth, aa = wrinkled). If there are 9 smooth plants (AA), how many heterozygotes (Aa) are present in the population?

Accepted Answer

42

Question 3

Which of the following is NOT an assumption of the Hardy-Weinberg equilibrium?

Accepted Answer

Small population size

Question 4

Which type of selection is illustrated by human birth weight, where infants of average weight have higher survival than those at either extreme?

Accepted Answer

Stabilizing selection

Question 5

In a population, the allele frequencies for a gene with three alleles are $$p = 0.5$$, $$q = 0.3$$, and $$r = 0.2. $$What is the expected frequency of the heterozygote genotype $$pq$$ under Hardy-Weinberg equilibrium?

Accepted Answer

$$2pq = 2 	imes 0.5 	imes 0.3 = 0.3$$

Question 6

Which evolutionary force is most likely responsible for the random fixation of alleles in a small population following a drastic reduction in population size?

Accepted Answer

Genetic bottleneck

Question 7

Darwin’s finches experienced a severe drought that killed the main food plant. Birds with larger beaks survived because they could eat larger seeds. What type of selection does this scenario illustrate?

Accepted Answer

Directional selection

Question 8

Which of the following best describes gene flow?

Accepted Answer

Introduction of genes from one population to another through movement and reproduction

Question 9

Which scenario is most likely to result in speciation due to pre-zygotic isolation?

Accepted Answer

Populations are separated by a mountain range and cannot interbreed

Question 10

Which of the following statements about dominant alleles in Hardy-Weinberg populations is correct?

Accepted Answer

Dominance or recessiveness does not affect allele frequency

Question 11

A population of fish is split into two groups by a dam. Over time, the two groups accumulate genetic differences and can no longer interbreed. What evolutionary process has occurred?

Accepted Answer

Speciation

Question 12

Which of the following is a post-zygotic barrier to reproduction?

Accepted Answer

Hybrid nonviability

Question 13

Which of the following is most likely to increase genetic diversity in a population?

Accepted Answer

Mutation

Question 14

Which equation correctly represents the relationship between allele frequencies and genotype frequencies for a gene with two alleles under Hardy-Weinberg equilibrium?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 15

A small group of birds migrates to a new island and establishes a population. Over generations, the new population has reduced genetic diversity compared to the original population. What is this phenomenon called?

Accepted Answer

Founder effect

Question 16

Which of the following best explains why small populations are more susceptible to genetic drift?

Accepted Answer

Random fluctuations in allele frequencies have a larger impact

Question 17

Which type of selection favors individuals at both extremes of a phenotypic trait over those with intermediate values?

Accepted Answer

Disruptive selection

Question 18

Which of the following is an example of macroevolution?

Accepted Answer

Emergence of a new species due to reproductive isolation

Question 19

Which process is most likely to lead to fixation of homozygous alleles in a population?

Accepted Answer

Genetic drift in small populations

Question 20

Which of the following is a direct consequence of a genetic bottleneck?

Accepted Answer

Reduced genetic diversity

Population Genetics and Evolution: Mechanisms of Allele Frequency Change - nov 12

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