In cats, black fur colour is determined by an X-linked allele; the other allele at this locus determines orange colour. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
A) tortoiseshell females; tortoiseshell males
B) black females; orange males
C) tortoiseshell females; black males
D) orange females; black males

Question

Quizplus · Accepted Answer

The black female is XBXB (X-linked allele for black on both X chromosomes) and the orange male is XBY (X-linked allele for orange on X chromosome and Y-linked allele for orange on Y chromosome). 
The possible gametes of the black female are Xb and Xb, and the possible gametes of the orange male are XY and XbY. 
The offspring genotypes can be: XbXbY (black male), XBXbY (tortoiseshell male), XbXb (black female), and XBXb (tortoiseshell female). 
Therefore, the expected offspring are tortoiseshell females and black males.

In Cats, Black Fur Colour Is Determined by an X-Linked