Question

Alkaptonuria is caused by a mutation that renders the enzyme homogentisate dioxygenase incapable of carrying out the reaction to break down homogentisic acid. Archibald Garrod observed that the disease often manifested in one or more siblings but not in the parents and that it was more common in marriages between first cousins. What did these observations suggest to him?

Answer 1

These observations suggested that alkaptonuria is an autosomal recessive disorder where child suffering from the disease inherits two mutated genes, one from each parent and both the parents are considered carriers. Thus This disorder is usually passed on by two carriers. Their health is rarely affected, but they have one mutated gene (recessive gene) and one normal gene (dominant gene) for the condition. This is also the reason why it was more common in marriages between first cousins.