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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 will be:
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The correct answer is:
2 yellow : 1 grey
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
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).
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).
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