Which of the following is controlled by a recessive gene in humans?

In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased? (In $ \%$ )

Pick out the correct statements.
$(1)$ Haemophilia is a sex-linked recessive disease.
$(2)$ Down's syndrome is due to aneuploidy.
$(3)$ Phenylketonuria is an autosomal recessive gene disorder.
$(4)$ Sickle cell anaemia is an $X$-linked recessive gene disorder.

Phenylketonuria is caused by the deficiency of which enzyme?

Cystic fibrosis,Myotonic dystrophy,and Thalassemia are:

If a colour blind woman marries a normal visioned man,their sons will be