Population Genetics (College Board AP® Biology): Exam Questions

In a large population of fruit flies, the frequency of an allele for eye color remains constant at 0.3 across many generations, despite no apparent selective advantage.

Which of the following best explains this stability in allele frequency?

The ability to roll one’s tongue is under the control of a single gene. The gene has two alleles R and r. People who can roll their tongue can have the genotypes RR or Rr. People who cannot roll their tongue have the genotype rr. A survey showed that 12 % of the student population in a single school could not roll their tongues. A student used the Hardy-Weinberg equations below to calculate the number of heterozygous individuals in the school:

p + q = 1

p² +2pq + q² = 1

Which of the following represents the percentage of heterozygous individuals at the student’s school?

A population of lizards (Anolis sagrei) colonized a small Caribbean island. The lizards had originally been part of a larger population on another nearby island. A team of geneticists compared the diversity of scale color alleles of the recently founded population with those of the larger source population. The frequency of scale color alleles in both populations is shown in Figure 1 below.

Which of the following conclusions is best supported by the data?

A population geneticist studied allele frequencies in a small, isolated population of butterflies over several generations. The frequency of a recessive allele for wing pattern was tracked, and the results are shown in Figure 1 below.

Which of the following processes is most likely to be responsible for the observed pattern of allele frequency changes?

Researchers studying a population of seed-eating finches on Daphne Major island in the Galapagos measured the beak depths of all finches on the island in 1976, then again in 1978 after a severe drought. A result of the drought was an increase in the number of large, tough seeds and a decrease in the number of small, soft seeds on the island. The beak depth measurements and population size before and after the drought are shown in the table below.

Which of the following best explains the change in mean beak depth from 1976 to 1978?

Sea otters are marine mammals that were hunted extensively for their fur during the 18th and 19th centuries. Geneticists have studied the genetic structure of sea otter populations using DNA samples from pre-fur trade otter populations and modern otter populations. The study looked at variation in the length of nuclear microsatellite DNA; short, repeating base sequences that can be located within the alleles of genes. Figure 1 compares the frequency of different forms of the Lut 453 microsatellite in pre- and post-fur trade otter populations.

Which of the following claims is best supported by the data in Figure 1?

Figure 1 below represents the expected allele frequencies and genotypes of a population under the Hardy-Weinberg principle.

Which of the following correctly describes the population in Figure 1?

In the Hardy-Weinberg equation the frequency of the dominant allele is represented by p. A group of scientists used a mathematical model to predict the frequency of p in the next generation of a population, assuming that the starting frequency of p was 0.5. They calculated the predicted frequency of p in a population with:

• 10 individuals

• 100 individuals

• 1000 individuals

Figure 1 shows the resulting predictions using the mathematical model. Population size is represented by N.

Which of the following correctly states the effect of population size on predicted frequency of p in a subsequent generation?