Which of the following is an example of a sex-linked disease?

In a normal couple,half of the sons are hemophilic and half of the daughters are carriers. Where is the gene located?

Assertion $(A) :$ Phenylketonuria is an inborn error of metabolism and inherited as the autosomal dominant trait.
Reason $(R) :$ The disease is caused by mutation in the gene that codes for the enzyme phenylalanine hydroxylase.

The most common type of haemophilia results from the congenital absence of

If a colour blind lady marries a normal man,their children will be:

$A$ couple,both carriers for the gene of sickle cell anaemia,are planning to get married. What are the chances of them having an anaemic child (in $\%$)?