Which of the following human diseases provides an example of sex-linked inheritance?

$A$ colour blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson being colour blind?

Given below are the two statements.
Statement $I$: Widow's peak is determined by an autosomal dominant gene.
Statement $II$: Heterozygous individuals have a straight hairline.
In the light of the above statements,choose the correct answer from the options given below:

Sickle-cell anaemia has not been eliminated from the African population because it

What will be the genotypes of the parents of a colorblind daughter and a colorblind son?

$A$ colour-blind man marries the daughter of a colour-blind person. Then in their progeny: