Exam 7: The Genetics of Populations

Under mutation-selection balance, even if an allele has a selective advantage it will never be fixed in a population. Explain why this is true.

Stalk height in sunflowers is determined by two alleles at a locus, T and t, which display incomplete dominance. TT individuals are tall, Tt are medium, and tt are short. In a population that is in Hardy-Weinberg equilibrium, we count 1,546 short plants out of 9,666. How many plants do you expect to be tall?

The table shows the survival and seed production of hybrid and wild sunflowers at three different sites. What do these data demonstrate?

The graph shows the relationship between the number of surviving gray wolf pups in a litter and the inbreeding coefficient of those pups. What do these data reveal about the types of alleles present in this population?

The figure shows the allele frequency trajectories for two populations starting from two different initial frequencies. Which evolutionary processes could produce this result?

Why do you need to use a statistical test (e.g., the chi-square test) to compare the observed genotype frequencies in a population to those expected under Hardy-Weinberg equilibrium?

Inbreeding increases the frequency of ________ in a population.

Which of the following is a consequence of recessive deleterious alleles in a population?

Considering any field of science, why is it useful to have a null model, and how is a null model applied?

The null model for population genetics is

What does it mean for two alleles to be identical by descent?

Does mutation change genotype frequencies from Hardy-Weinberg equilibrium? Why or why not?

Consider a population that is in Hardy-Weinberg equilibrium at a locus with two alleles, A and a, at frequencies of p and q, respectively. Assuming the population remains in Hardy-Weinberg equilibrium, what is the expected frequency of Aa heterozygotes after 100 generations?

Mathematical descriptions of evolutionary processes allow biologists to make ________ predictions about how genotype frequencies change over time.

In the scenario depicted in the figure, what will happen to the allele frequencies on the island? Assume there is no selection or mutation, mating is random, and the population sizes are large.

What are the effects of natural selection, mutation, and migration on the amount of genetic variation within and between populations?

Consider a locus with two alleles in an island population, where all assumptions of the Hardy-Weinberg model are met except "no migration." The figure shows the change in the frequency of the A₁ allele over several generations. What can you say about the population that is the source of migrants to the island?

Why is underdominance so rare in natural populations?

Consider a locus with two alleles, A and A) If the rate of mutation of A to a is 0.0000025 and the rate of mutation of a to A is 0.0000010, what will be the equilibrium frequency of the A allele? (Recall that the equilibrium allele frequency under mutation is p v v, where p is the equilibrium frequency of the A allele,  is the rate of mutation from A to a, and v is the rate of mutation from a to

Population sex ratios, that is, how many males and females there are in a population, are most likely influenced by which process?