Sickle cell anemia and Huntington's chorea are both ..........

Haemophilia is a:

$A$ woman has a haemophilic son and three normal children. What is the genotype of the woman and her husband?

Both husband and wife have normal vision,though their fathers were colour blind and their mothers did not have any gene for colour blindness. The probability of their daughters becoming colour blind is (in $\%$)

$A$ normal woman,whose father was colour blind,marries a normal man. What is the chance of occurrence of colour blindness in the progeny (in $;\%$)?

Color blindness is caused by: