Question

A person with the genetic disorder Klinefelter's syndrome has an extra x-chromosome. Affected individuals have the genotype XXY. What can you infer is most likely the genetic mutation that results in Klinefelter's syndrome?

Answer 1

In the human, the presence of one Y chromosome produces male secondary sex characteristics in the absence of specific mutations for sex determining loci. Since the child must get his Y chromosome from his father, the nondisjunction that produces a Klinefelter syndrome child could occur in either meiotic division of the mother, but could only occur in the first meiotic division in the father. If nondisjunction occurred in the father, the zygote would have to get both an X and a Y chromosome in the same sperm. In spermatogenesis this could only result from a mistake in first division. Second meiotic division of spermatogenesis separates either the two X chromatids into different gametes or the two Y chromatids into different gametes.

Answer 2

I already find out , but thanks :) @mgb20