Haemophilia is a type of genetic disorder that is:

What is the full form of $PKU$?

If a father and son are both defective in red-green colour vision,is it likely that the son inherited the trait from his father? Comment.

What is the cause of sickle cell anemia?

Given below are two statements:
Statement $I$: The son of a carrier woman has a $100$ percent chance of being colour blind.
Statement $II$: $A$ daughter of a carrier mother and a normal father will be $100$ percent colour blind.
In the light of the above statements,choose the correct answer from the options given below:

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