AN XXY MALE IN THE MOUSE

Abstract

An XXY mouse was de-tected by sex-linked markers and studied cytologically. The genotype is + sf/Ta +/Y or +/Ta +/Y. The expression of Ta is not affected by the Y. The exceptional animal is viable, of normal size, and of male phenotype, though sterile. Since XTa and Y are both derived from the father, the XXY male provides proof of nondisjunction in meiosis of the male mouse. This event is apparently rare compared with events that lead to sex-chromosome loss only (in meiosis or cleavage), as indicated by the relatively much smaller frequency of XMX?Y (0.02%) than XMO (0.76%) in crosses where these can be detected simultaneously.