What is the cause of haemophilia
Chromosomal aberration
Somatic mutation
$X$-linked mutation
All the above
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
Which one is the incorrect statement with regard to the importance of pedigree analysis?
A colour blind man marries the daughter of a colour blind person. Then in their progeny
If a colour blind woman marries a normal visioned man, their sons will be