Question

A woman with two genes, one for haemophilia and one for colour blindness on one of its X-chromosomes marries a normal man. What percentage of sons will be normal and affected by both colourblindness & haemophilia?

• A. All sons haemophilic and colour blind
• B. 50% colourblind and haemophilic sons, 50% normal sons
• C. All daughters haemophilic and colour blind
• D. 50% haemophilic daughters and 50% colour blind daughters

Answer 1

The correct option is B 50% colourblind and haemophilic sons, 50% normal sons

After performing the cross between a woman with two genes, one for haemophilia and one for colour blindness on one of its X-chromosomes with a normal man having XY chromosome the resultant progeny will be 50% colourblind and haemophilic sons, 50% normal sons.

	$X$	$Y$
$X^{hc}$	$X^{hc}$$X$	$X^{hc}$$Y$
$X$	$XX$	$XY$