A gene on the Y chromosome causes a rare disease. A woman married to a man with the disease has three children. The first two are daughters without the disease. The third is a son. What is the probability that the son will have the gene?

Question

Quizplus · Accepted Answer

The gene causing the disease is on the Y chromosome, which sons inherit from their fathers. Since the son receives his Y chromosome from his father and the disease gene is on this chromosome, he will have a 100% chance of inheriting the gene.

A Gene on the Y Chromosome Causes a Rare Disease