Question

A colourblind man marry with a daughter of colourblind father, the generation will be

• A. There will be no daughter colourblind
• B. All sons will be colourblind
• C. All daughter will be colourblind
• D. Half of the sons will be colourblind

Answer 1

The correct option is D Half of the sons will be colourblind

$X^c$Y $X^c$X	$X^c$	Y
$X^c$	$X^c$$X^c$	$X^c$Y
X	$X^c$X	XY

• Colourblindness is X-linked recessive disorder and follows criss-cross inheritance.
• A colourblind man ($X^c$Y) and daughter of the colourblind father ($X^c$X) will obtain 1/4 colourblind daughters, 1/4 carrier daughters, 1/4 colourblind sons and 1/4 normal sons. Hence, half of the sons will be colourblind.
  So, the correct answer is option D.