Question

Black hair color is dominant to white hair color in mice. Determine the phenotypic ratio for the offspring of a heterozygous black mouse and a white mouse.

a) 4 Black: 0 White
b) 3 Black: 1 White
c) 2 Black: 2 White
d) 0 Black: 4 White

Answer 1

Grey fur

The inheritance of fur colour in mice is controlled by a single gene. White fur is recessive - a. Grey fur is dominant - A.

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Answer 2

Answer:

The phenotypic ratio of the progeny will be 2 Black: 2 White,  i.e. option (c) is the correct answer.

Explanation:

As we are provided in the question, Black hair is dominant over white hair color in mice.

Let's say the Black hair color allele is represented by 'B' and white hair color is represented by 'b'.

So, the genetic constitution of heterozygous black mice will be 'Bb' and that of white mice will be 'bb'.

Note - The alleles for recessive genes are always expressed only in homozygous conditions.

So ,we perform the cross between the two by using the  Punnet square method.

The gamates for heterozygous Black mice will be having 'B' and 'b' alleles whereas gametes for homozygous white mice will be having 'b' and 'b'.

So, the results after performing the cross will be as follows :

Bb - Heterozygous Black (50% progeny)

bb - Homozygous White ( 50% progeny)

So, on the basis of the above information, we can conclude that 2 will be black and 2 will be white.

So, the correct answer will be an option (c).