In mice, Y is the dominant allele for yellow fur and y is the recessive allele for grey fur. If Y in the homozygous form leads to death of mice, the result of cross Y y × Y y will be:

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Since the homozygous condition for Y allele is lethal, the individuals with genotype YY will not survive.

On crossing the parents with genotype Yy, the following progenies are possible.

Yy X Yy

	Y	y
Y	YY (Death)	Yy (Yellow)
y	Yy (Yellow)	Yy (Grey)

YY will give yellow fur but the progeny will not survive.

Yy will give yellow fur as Y is dominant and the progeny will survive since this combination is not lethal.

yy will give grey fur as it is recessive.

Phenotype ratio for the progenies will be 2:1 (2 yellow and 1 grey).

Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

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