Phenylketonuria is a rare recessive autosomal disease that r

Phenylketonuria is a rare recessive autosomal disease that results in brain damage if left untreated. About 1 in 10,000 people in the US is born with phenylketonuria. Assuming the US population is in HW equilibrium, what is the expected number of carriers per 10,000 people?

Solution

First estimate q from q²

q = square root of q² =square root of 1/10,000 = square root of 0.0001 = 0.01

Therefore, p = 1 - q = 1 - 0.01 = 0.99

Now Using Hardy-Weinberg Law, expected number of individuals of each genotype can be calculated as

DD = p² = 0.9810

Dd = 2pq = 0.0198

dd = q² = 0.0001

Therefore, 1.98% of the population is expected to be carriers