Which disease is caused by a point mutation?

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

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

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:

$A$ person whose father is colourblind marries a lady whose mother is the daughter of a colourblind man. Their children will be:

Mark the correct statement with respect to sickle-cell anaemia.