Chapter 21, Problem 9P

Alkaptonuria is a recessive autosomal genetic disorder associated with darkening of the urine. In the United States, approximately 1 out of every 250,000 people has alkaptonuria.

a.	Assuming Hardy-Weinberg equilibrium, estimate the frequency of the allele responsible for this trait.
b.	What proportion of people in the U.S. population are carriers for this trait? In this population, what is the ratio of carriers to individuals affected by alkaptonuria?
c.	If a woman without alkaptonuria had a child with this trait with one husband then remarried, what is the chance that a child produced by her second marriage would have alkaptonuria?
d.	Alkaptonuria is a relatively benign condition, so there is little selective advantage to individuals with any genotype; as a result, your assumption of Hardy-Weinberg equilibrium in part (a) is reasonable. Could you also use the assumption of Hardy-Weinberg equilibrium to estimate the allele frequencies and carrier frequencies of more severe recessive autosomal conditions such as cystic fibrosis? Explain.