Question

6. A brown-eyed man, whose mother was blue-eyed, marries a blue-eyed woman. The man is red-green colour blind and his wife has normal colour vision although her father was also colour blind. (Note: brown eyes is dominant over blue eyes and eye colour is inherited autosomally. Red-green colour blindness is a sex-linked recessive trait). a) What are the genotypes of the man and his wife with respect to these two traits? Ger

also draw the punnet square

Answer 1

Let B be the allele of the brown eye and b for the blue eye.

Color blindness is an X-linked recessive genetic disorder.

the male has one X-chromosome and a female has two X-chromosomes. The male receives his only X-chromosome from his mother and the female reived one X chromosome from her father and one from her mother. let Xc be the allele for colorblindness and X for the normal eye.

Given that the mother of the brown eye man has blue eyes. So he is heterozygous for the brown color.

So genotype of man is BbX^cY and female is bbX^cX

B-

:

Female bbX-X ВЫХсү male bxe bX BX BY EXC by bX BXC BbXcx bX BbXX bbXX BbXY bX bbxcx BY BbXY bbXY by bbXY

C - Expected Genotype ratio - BbX^cX^c : BbXX^c : bbX^cX^c : bbXX^c : BbX^cY : BbXY : bbX^cY : bbXY is 1:1:1:1:1:1:1:1

Expected Phenotype - Brown eye and normal vision female: Brown eye and Colorblind female: Blue eye and normal vision female: Blue eye and Colorblind female : Brown eye and normal vision male: Brown eye and Colorblind male : Blue eye and normal vision male: Blue eye and Colorblind male is 1:1:1:1:1:1:1:1