Question

A colour-blind man marries a woman who is carrier for haemophilia. Which of the following is true for their progenies?

• A. 25% of the progenies carry the genes for both haemophilia and colour-blindness
• B. 25% of the progenies carry only the gene for haemophilia
• C. 25% of the progenies carry only the gene for colour-blindness
• D. All of these

Answer 1

Answer: (D)

Genotype of Male is $X_{c}Y$ and Genotype of Female is $X_{h}X$ .
The genotypes of their children will be

	$X_c$	$Y$
$X_h$	$X_c{X}_h$	$X_{h}Y$
$X$	$X_{c}X$	$XY$

Their children $X_{c}X$ (daughter carrier for colourblindness),
$X_c{X}_h$ (daughter carrier for colourblindness and haemophilia), XY (normal son), $X_{h}Y$ (haemophiliac son)
Thus, 25% of their children will carry the genes for both haemophilia and colour-blindness $X_c{X}_{h,}$ 25% of their children will carry the gene only for haemophilia $X_{h}Yand$ 25% of the progenies carry only the gene for colour-blindness $X_{c}X$