What is the most likely reason that alkaptonuria is a recessive disease?
A) The mutant phenotype arises from a change in the protein's amino acid sequence.
B) More than half the typical amount of homogentisic acid oxidase is needed to break down the toxin by-product.
C) Having half the typical amount of homogentisic acid oxidase is sufficient to break down the toxin by-product.
D) Homogentisic acid oxidase occurs early in the metabolic pathway.
E) Homogentisic acid oxidase occurs late in the metabolic pathway.

Question

Quizplus · Accepted Answer

Alkaptonuria is caused by a mutation in the homogentisic acid oxidase gene, which results in a deficiency of the enzyme needed to break down homogentisic acid. This acid builds up in the body and can cause various symptoms, including darkening of urine, joint pain, and cartilage and heart valve problems. Since having half the typical amount of homogentisic acid oxidase is sufficient to break down the toxin by-product, it is likely that the disease is recessive. If the disease were dominant, only one copy of the mutated gene would be needed for the disease to manifest. However, with a recessive inheritance pattern, an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease.

What Is the Most Likely Reason That Alkaptonuria Is a Recessive