Chapter 21, Problem 12P

a.

Alleles of genes on the X chromosome can also be at equilibrium, but the equilibrium frequencies under the Hardy-Weinberg assumptions must be calculated separately for the two sexes. For a gene with two alleles A and a at frequencies of p and q, respectively, write expressions that describe the equilibrium frequencies for all the genotypes in men and women.

b.

Approximately 1 in 10,000 males in the United States is afflicted with hemophilia, an X-linked recessive condition. If you assume that the population is at Hardy-Weinberg equilibrium, what proportion of American females would be hemophiliacs? About how many female hemophiliacs would you expect to find among the 170 million women living in the United States? (Assume that all females with hemophilia are homozygous for the disease allele.)