X and Y chromosome pairing and disjunction in a male mouse with an XYY sex-chromosome constitution

Abstract

In an albino mouse with the usual phenotypic appearance, an XYY polysomy was observed in the germinal epithelium. Analysis of all three metaphase stages verified this observation. At metaphase I, in addition to XYY, XYY, and XYY bi- and univalent groupings, XYY trivalent configurations were present. The data indicated randomness in association of the X and Y and random segregation of the three chromosomes. From the relative frequency of the different metaphase stages, it was concluded that only a fraction of the metaphase I cells reached metaphase II.