A normal woman whose father was colourblind. marries a normal man. What kinds of children can be expected and in what proportion?

Which one of the following symbols represents mating between relatives in human pedigree analysis?

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

What is the cause of haemophilia