A couple has a child with Harman's ataxia (a recessive disorder).If this couple has second child,what is the probability that child will have ataxia?

Question

Quizplus · Accepted Answer

Harman's ataxia is a recessive disorder, which means that for a child to have ataxia, both parents must carry a copy of the recessive gene. If the first child has ataxia, then we know that both parents are carriers of the recessive gene. Therefore, the probability that the second child will have ataxia is 1/4 or 25%. This is because there are four possible outcomes for the second child's genotype: Hh (carrier), HH (not a carrier), hh (affected), and Hh (carrier). Only one of these outcomes (hh) results in the child having ataxia.

A Couple Has a Child with Harman's Ataxia (A Recessive