Red-green colour blindness appears due to

The amino acid substituted in sickle cell anaemia is

Sickle cell anaemia is

$A$ color-blind man marries a woman with normal vision,whose family has no history of color blindness. What is the probability that their daughter's children (grandsons and granddaughters) will be color-blind?

Match Column-$I$ with Column-$II$ and select the correct option.

Column-$I$	Column-$II$
$(P)$ Haemophilia	$(i)$ Recessive gene: $X^{h}X^{h}$
$(Q)$ Colour blindness	$(ii)$ Recessive gene: $pp$
$(R)$ Phenylketonuria	$(iii)$ Recessive gene: $Hb^{s}Hb^{s}$
$(S)$ Sickle-cell anaemia	$(iv)$ Recessive gene: $X^{c}X^{c}$

$A$ woman with normal vision marries a man with normal vision and gives birth to a color-blind son. Her husband dies,and she remarries a color-blind man. What is the probability of color blindness in her children from the second marriage?