In cats an X-linked pair of alleles, B and b, controls color of fur. The alleles are incompletely
dominant: B produces black, b produces yellow, and Bb produces tortoise-shell.
(a) A yellow cat had a litter of two tortoiseshell kittens and one yellow. What is the sex of
the yellow kitten?
(b) A tortoiseshell cat brings home a litter of black, yellow, and tortoiseshell kittens. The
color of which sex would tell you the color of the tomcat that produced them?
(c) A yellow male is crossed with a tortoiseshell female. If the female has all male kittens in
her litter of four, what color(s) would they be?
(d) A tortoiseshell cat brings home her litter of black, yellow, and tortoiseshell kittens. By
what method could you possibly decide whether the male parent was the black tomcat
next door? What will be an ideal response?
Question 2An X-linked recessive gene (c) produces red/green color blindness. A normal woman whose father
was color blind marries a color-blind man.
(a) What are the possible genotypes for the mother of the color-blind man?
(b) What are the possible genotypes for the father of the color-blind man?
(c) What are the chances that the first son will be color-blind?
(d) What are the chances that the first daughter will be color-blind? What will be an ideal response?
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