Question

If someone was born with Jacob’s syndrome (XYY), in which parent and when nondisjunction happened during gamete formation?

Answer 1

Nondisjunction occurred during spermatogenesis in the father. The mother always provides an X chromosome. The gender of the child is determined by whichever sex chromosome (X or Y) was given from the father. It is only possible for a Y chromosome to come from the father.
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