Two intersex dogs with mosaicism.

Two intersex dogs with various degrees of mosaicism in the somatic tissues are described. Normal female cells as well as Y-bearing cells with aneuploidy and other abnormalities were involved. In the Red setter an ovarian cortex had developed in mosaic gonads with 8 and 10% of Y-bearing cells. Slight masculinization of the medullae corresponded with some external virilization. These observations support the existence of a threshold proportion of Y-bearing cells for testicular differentiation. Fragments of chromatin in 36% or fewer of the cells in the Cocker spaniel may have been translocated Y-chromosome material.