If a colour­blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour­blind is

Haemophilia $A$ is due to the absence of

Following characters are indicate

$(i)$ presence of sickle - shaped $RBC$

$(ii)$ Blood not clot, non stop bleeding

$(iii)$ The heterozygous female transmit the disease to sons.

$(iv)$ Both heterozygous parents transmit the disease to offspring

A colourblind daughter is born when

In which of the following colourblindness is inherited

If a man who is colour blind marries a women, who is pure normal for colour vision, the chances of their sons have colour blindness is