| Y chromosome (testes) | No Y chromosome (absence of testes) |
---|---|---|
One X chromosome (scrotum) | XY | XO |
 | Male animals with scrotum and testes | Animals without testes and an empty scrotum instead of a pouch |
Two X chromosomes (pouch and mammary glands) | XXY | XX |
 | Animals with testes and a pouch with mammary glands instead of scrotum | Female animals with a pouch and mammary glands |