A couple has just been informed that one of them has Huntington's disease, and that the other spouse does not have a disease allele. With this information, what is the chance that at least one of their two young children has a disease allele?

Question

Quizplus · Accepted Answer

Huntington's disease is an autosomal dominant condition, meaning that having just one copy of the disease allele (from the affected parent) is enough for a child to have a chance of developing the disease. Each child has a 50% chance of inheriting the disease allele from the affected parent. The probability that at least one of two children inherits the allele is calculated as 1 minus the probability that neither child inherits the allele. The probability that neither child inherits the allele is 0.5 (chance one child doesn't inherit) * 0.5 (chance the second child doesn't inherit) = 0.25. Therefore, the probability that at least one child inherits the allele is 1 - 0.25 = 0.75 or 75%.

A Couple Has Just Been Informed That One of Them