Question

A male mouse with a pale yellow coat called cream is mated to a female mouse with a wild-type gray- brown coat. All of the F₁ mice, both males and females have the wild-type gray-brown color. One of these F₁ female mice is mated to cream-colored male.

             a. What are the expected results if cream is X-linked and recessive?

2. What are the expected results if cream is autosomal and recessive?
3. In fact, cream is X-linked. When the F₁ female mouse is examined more closely, it is apparent that she has patches of fur that are cream colored rather than gray-brown. Explain this result.

Answer 1

1. Male mouse yy cream coat colour x Female mouse YY wild type grey brown coat colour

Yy brown coat colour F1   

Yy X yy F1 is crossed with Recessive   

Yy (2) yy (2) Brown 2; Cream 2 1;1 test cross

a) female X^YX^Y x X^y Y

X^YXy female with brown coat colour (2) and X^Y Y male with brown coat colour. (2)

(b) male mouse yy , results will be same as F1 and Test cross gi venmale with brown coat colour

(c)This shows that two alleles are required to give brown colour withY and one y she had pattches of cream  

colour.