Successive Non-Disjunction at First and Second Meiotic Division of Spermatogenesis: Evidence of Chromosomes and Xg

Abstract

An Xg(a+) male with XXYY sex chromosomes was the son of an Xg(a+) father and an Xg(a—) mother with normal chromosomes. This seems to be the first example in which there is good evidence of non-disjunction at the first and second meiotic division of paternal spermatogenesis, giving rise to an XYY sperm which fertilized a normal ovum. Other explanations are discussed.