Sickle cell anaemia is due to

Given below is a pedigree chart showing the inheritance of a certain sex- linked trait in humans.

The trait traced in the above pedigree chart is

The character of organisms is said to be sex linked when its gene is carried on

A normal­visioned man whose father was colour­ blind, marries a woman whose father was also colour­blind. They have their first child as a daughter. What are the chances that this child would be colour­ blind ?

Pick out the correct statements.

$I.$ Haemophilia is a sex-linked recessive disease

$II.$ Down's syndrome is due to aneuploidy

$III.$ Phenylketonuria is an autosomal dominant gene disorder

$IV.$ Phenylketonuria is an autosomal recessive gene disorder

$V.$ Sickle cell anaemia is an $X$-linked recessive gene disorder

A woman has a haemophilic son and three normal children. Her genotype and that of her husband with respect to this gene would be