Haemophilia is caused due to the lack of:

Sir Archibald Garrod is associated with which of the following fields?

Sickle-cell anemia is caused by a change in which of the following?

Given below are the two statements.
Statement $I$: Widow's peak is determined by an autosomal dominant gene.
Statement $II$: Heterozygous individuals have a straight hairline.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following most appropriately describes haemophilia?

Alkaptonuria is a disease where the urine is: