A woman with normal vision, but whose father was colour blind, marries a colour blind man. Suppose that the…
A woman with normal vision, but whose father was colour blind, marries a colour blind man. Suppose that the fourth child of this couple was a boy. This boy:
may be colourblind or may be of normal vision
must be colour blind
must have normal colour vision
will be partially colour blind since he is heterozygous for the colourblind mutant allele.
Solution
The woman has normal vision but her father was colour blind so she should be the carrier to the disease as Colour blindness is an X-Linked recessive disorder.
The genotype of the woman would be: $22 \mathrm{AA}+\mathrm{XX}^{\mathrm{C}}$
The genotype of man to be colour blind should be: $22 \mathrm{AA}+\mathrm{X}^{\mathrm{C}} \mathrm{Y}$
The probability of Male child to be colour blind will $50 \%$ and the ratio of diseased to a normal male child is $1: 1$.
The probability of Male child to be colour blind will $50 \%$ and the ratio of diseased to a normal male child is $1: 1$.