Question

In mice, Y is the dominant allele for yellow fur and y is the recessive allele for grey fur. If Y is lethal when homozygous, then the result of cross Yy × Yy will be

• A. 3 Yellow: 1 Grey
• B. 2 Yellow: 1 Grey
• C. 1 Yellow: 1 Grey
• D. 1 Yellow: 2 Grey

Answer 1

The correct option is B 2 Yellow: 1 Grey

Explanation – As homozygous Y is lethal, YY mouse cannot live.

$\begin{array}{ccc}\downarrow \text{MICE 1/MICE 2}\to & \text{Y}& \text{y}\\ \text{Y}& \text{YY; Die(Homozygous dominant)}& \text{Yy; Yellow}\\ \text{y}& \text{Yy; Yellow}& \text{yy; Grey}\end{array}$