A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children ($2$ daughters and $5$ sons). Three of the sons suffer from the given disease but none of the daughters are affected which of the following mode of inheritance do you suggest for this disease

Linked gene are separated by

Mental retardation in man, associated with sex chromosomal abnormality is usually due to

A female with $XXXX$ chromosome will have the following number of Barr bodies

$A$ : Myotonic dystrophy is caused by recessive mutant pleiotropic gene.
$R$ : Gene mutation leads to more synthesis of fibrillin proteins.