Congenital retroflexion of the penis and inguinal cryptorchidism in a presumptive bovine twin with a 60,XY/60,XX/61,XX,+cen chromosome constitution.

Studies were carried out on a yearling Holstein with external genitalia resembling those of a freemartin whose birth and developmental history was unknown. Dissection following slaughter showed testes close to the external inguinal rings, an underdeveloped penis coiled up subcutaneously in the perineum and terminating in a deep fossa at the level of the ischial arch and no evidence of a female genital tract. Chromosome analyses showed 60,XY cells in the blood and 60,XX and 61,XX,+cen cells in other tissues. It is postulated that the animal had a basic 60,XX/61,XX+cen mixoploid chromosome constitution, that the centric fragment functioned as a Y chromosome or as an autosomal modifier of the X chromosome in sex determination which accounted for the animal's Klinefelter syndrome-like abnormalities, and that animal was also twin to a bull which accounted for the presence of 60,XY cells in the blood.