Question

One of the genes that controls color vision is found on the X chromosome. The dominant allele results in normal color vision, and the recessive allele causes colorblindness. Ginny has normal color vision and is heterozygous, but Harry is colorblind. If Ginny and Harry have three children, what is the probability that at least one of them is a colorblind son?A. 0 B. 1/8 C. 9/64 D. 3/8 E. 27/64.

Answer 1

Answer:

1/4

Explanation:

The trait is X-linked and recessive. A male only need one recessive allele to be affected while a female needs 2 recessive alleles to be affected.

Let the color vision allele be C.

Ginny is heterozygous, her genotype will be $X^C X^c$

Harry is color blind, his genotype will be $X^c Y$

If Ginny and Harry mate, their offspring's genotype will be: $X^C X^c, X^C Y, X^c X^c, X^c Y$

$X^C X^c$ is a heterozygous female with normal vision

$X^C Y$ normal vision male

$X^c X^c$ color blind female

$X^c Y$ color blind male

Probability of having a color blind child = 1/2

Probability of having a son = 1/2

Probability of having a colorblind son = probability of having a colorblind child and probability of the child being a son

       = 1/2 x 1/2

               = 1/4

The probability of at least one of the children being a colorblind son is 1/4

Answer 2

Answer:

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