A normal woman whose father was colourblind is married to a normal man, (assuming equal distribution of female gametes), then _________.

Question

TestHub · Accepted Answer

Colour blindness is an X-linked recessive trait.

Let $X^{C}$ be the normal allele and $X^{c}$ be the allele for colour blindness.

The woman's father was colourblind ( $X^{c} Y$ ), so he passed the $X^{c}$ chromosome to her. Since she is normal, her genotype is $X^{C} X^{c}$ (carrier).

The normal man has the genotype $X^{C} Y$ .

A cross between the carrier woman ( $X^{C} X^{c}$ ) and the normal man ( $X^{C} Y$ ) produces the following offspring:

Daughters: $X^{C} X^{C}$ (normal) and $X^{C} X^{c}$ (normal carrier).

Sons: $X^{C} Y$ (normal) and $X^{c} Y$ (colourblind).

Since the sons receive their X chromosome from the mother, who produces $X^{C}$ and $X^{c}$ gametes in equal proportions, $50%$ of the sons will be normal and $50%$ will be colourblind.

Answer: $50%$ of their sons will be colourblind.

Biology - Principles of Inheritance and Variation Question with Solution | TestHub

Options:

Doubts & Discussion