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In cats, tortoiseshell coat color appears in females. A tortoiseshell coat has patches of dark brown fur and patches of orange fur that each in total cover about half the body but have a unique pattern in each female. Male cats can be either dark brown or orange, but a male cat withtortoiseshell coat is rarely produced. Two sample crosses between males and females from pure-breeding lines produced the tortoiseshell females shown.
a. Explain the inheritance of dark brown, orange, and tortoiseshell coat colors in cats.
b. Why are tortoiseshell cats female?
c. The genetics service of a large veterinary hospital gets referrals for three or four male tortoiseshell cats every year. These cats are invariably sterile and have under-developed testes. How are these tortoiseshell male cats produced? Why do you think they are sterile?
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