A man has a condition where all of his gametes undergo nondisjunction of the sex chromosomes in meiosis I, but meiosis II proceeds normally. He mates with a woman who produces all normal gametes. What is the probability that the fertilized egg will develop into a child with Klinefelter syndrome (XXY)? Assume that all gametes and zygotes are viable.
A) 1/8
B) 1/4
C) 1/3
D) 1/2
E) 0

Question

Quizplus · Accepted Answer

In meiosis I nondisjunction, the man's gametes will be either XX or YY. When these combine with the woman's normal X gamete, the possible zygotes are XXY (Klinefelter syndrome) or XYY. Thus, the probability of XXY is 1/2.

A Man Has a Condition Where All of His Gametes