In Figure 20-5, note that the difference in survival rates between AS and AA genotypes declines as children get older. Offer one possible explanation for this observation.

Examining Figure 20-8, explain why the rate of evolution at nonsynonymous sites is lower. Do you expect this to be true only of globin genes or of most genes?

From Table 20-3, would you expect the noncoding mutation g4205a to be fixed before or after the coding mutation G238S in a population of bacteria evolving resistance to the antibiotic cefotaxime? Give at least two reasons for your answer.

Examining Table 20-4, what do you think would be the order of mutations fixed during selection in a third evolving virus line? Would the mutations become fixed in the same order as the TX or ID virus?

Examining Table 20-5, how would the interpretation of the McDonald–Kreitman test results differ if the number of nonsynonymous observed species differences was 1 instead of 7?

Using Figure 20-17, explain how the mutation in the GATA sequence of the Duffy gene imparts resistance to P.vivax infection.

In Figure 20-18, what is the evidence that polyploid formation has been important in plant evolution?

Compare Darwin’s description of natural selection as quoted in Section 10.1 with Wallace’s description of the tendency of varieties to depart from the original type quoted below it, on the same page. What ideas do they have in common?

What are the three principles of the theory of evolution by natural selection?

Why was the neutral theory of molecular evolution a revolutionary idea?

What would you predict to be the relative rate of synonymous and nonsynonymous substitutions in a globin pseudogene?

Are AS heterozygotes completely resistant to malarial infection? Explain the evidence for your answer.

If the mutation rate to a new allele is 10^–5, assuming there is no migration, how large must isolated populations be to prevent chance differentiation among them in the frequency of this allele?

Glucose-6-phosphate dehydrogenase (G6PD) is a critical enzyme involved in the metabolism of glucose, especially in red blood cells. Deficiencies in the enzyme are the most common human enzyme defect and occur at a high frequency in certain populations of East African children.

Large differences in Hb^S frequencies among Kenyan and Ugandan tribes had been noted in surveys conducted by researchers other than Tony Allison. These researchers offered alternative explanations different from the malarial linkage proposed by Allison. Offer one counterargument to, or experimental test for, the following alternative hypotheses:

How many potential evolutionary paths are there for an allele to evolve six different mutations? Seven different mutations? Ten different mutations?

The MC1R gene affects skin and hair color in humans. There are at least 13 polymorphisms of the gene in European and Asian populations, 10 of which are nonsynonymous. In Africans, there are at least 5 polymorphisms of the gene, none of which are nonsynonymous. What might be one explanation for the differences in MC1R variation between Africans and non-Africans?

Opsin proteins detect light in photoreceptor cells of the eye and are required for color vision. The nocturnal owl monkey, the nocturnal bush baby, and the subterranean blind mole rat have different mutations in an opsin gene that render it nonfunctional. Explain why all three species can tolerate mutations in this gene that operates in most other mammals.

Full or partial limblessness has evolved many times in vertebrates (snakes, lizards, manatees, whales). Do you expect the mutations that occurred in the evolution of limblessness to be in the coding or noncoding sequences of toolkit genes? Why?

Several Drosophila species with unspotted wings are descended from a spotted ancestor. Would you predict the loss of spot formation to entail coding or noncoding changes in pigmentation genes? How would you test which is the case?

It has been claimed that “evolution repeats itself.” What is the evidence for this claim from

What is the molecular evidence that natural selection includes the “rejection of injurious change”?

What are three alternative fates of a new gene duplicate?

What is the evidence that gene duplication has been the source of the α and β gene families for human hemoglobin?

DNA-sequencing studies for a gene in two closely related species produce the following numbers of sites that vary:

Does this result support neutral evolution of the gene? Does it support an adaptive replacement of amino acids? What explanation would you offer for the observations?

In humans, two genes encoding the opsin visual pigments that are sensitive to green and red wavelengths of light are found adjacent to one another on the X chromosome. They encode proteins that are 96 percent identical. Nonprimate mammals possess just one gene encoding an opsin sensitive to the red/green wavelength.

About 9 percent of Caucasian males are color-blind and cannot distinguish red-colored from green-colored objects.