Chapter 47, Problem 1ITD

The human AMY-1 gene encodes salivary amylase, an enzyme that breaks down starch. The number of copies of this gene varies, and people who have more copies generally make more of the enzyme. In addition, the average number of AMY-1 copies differs among cultural groups.

George Perry and his colleagues hypothesized that duplications of the AMY-1 gene would confer a selective advantage in cultures in which starch is a large part of the diet. To test this hypothesis, the scientists compared the number of copies of the AMY-1 gene among members of seven cultural groups that differed in their traditional diets. The Figure shows their results.

Starchy tubers are a mainstay of Hadza hunter-gatherers in Africa, whereas fishing sustains Siberia’s Yakut. Almost 60% of Yakut had fewer than 5 copies of the AMY-1 gene. What percentage of the Hadza had fewer than 5 copies?

FIGURENumber of copies of the AMY-1 gene among members of cultures with traditional high-starch or low-starch diets.

Source: G. Perry et al. 2007. Diet and the evolution of human amylase gene copy number variation. Nature Genetics 39:1256–1260.