A male pseudohermaphrodite with a dicentric Y chromosome. Autoradiographic study.

A 13-year-old male pseudohermaphrodite (mixed gonadal dysgenesis, unilateral testicular differentiation) was found to be a chromosomal mosaic of the 45, XO/46, XY type, the Y chromosome being a symmetrical dicentric chromosome. Presumed Y chromosomes similar to this one have been observed before, but their identification was not supported by autoradiographic data. In the present study the identification of the dicentric as a Y chromosome was supported by observing a relatively late DNA replication during the S period. The differentiation of testicular tissue on one side may be related to the presence of short arm material of the Y chromosome in the genome of the XY dic cells.