A disease is caused by homozygosity for the g allele (G is the corresponding wild-type allele).However, the penetrance of the disease is 75%.Two individuals known to be heterozygotes have a child.What is the probability that the child exhibits the disease?

Question

Quizplus · Accepted Answer

The probability that the child inherits the g allele from both parents (and is thus homozygous for the g allele) is 1/4, since each parent has a 1/2 chance of passing on the g allele. Given that the child is homozygous for the g allele, the penetrance of the disease is 75%, or 3/4. Therefore, the overall probability that the child exhibits the disease is 1/4 (chance of being homozygous gg) * 3/4 (penetrance) = 3/16.

A Disease Is Caused by Homozygosity for the G Allele