**Question:** All of the following statements about the genetics of G6PD deficiency are true, except -

A. G6PD deficiency is a single gene disorder.
B. G6PD deficiency is caused by a mutation in the X-chromosome.
C. G6PD deficiency is a common disorder in the Mediterranean region.
D. G6PD deficiency is a benign condition with no clinical consequences.

**Correct Answer: D. G6PD deficiency is a benign condition with no clinical consequences.**

**Core Concept:** G6PD deficiency is a common X-linked genetic disorder affecting the enzyme glucose-6-phosphate dehydrogenase (G6PD). G6PD is responsible for preventing oxidative stress in red blood cells by catalyzing the reduction of nicotinamide adenine dinucleotide phosphate (NADPH) and detoxifying reactive oxygen species (ROS).

**Why the Correct Answer is Right:** G6PD deficiency is a single gene disorder caused by mutations in the G6PD gene located on the X-chromosome. The deficiency leads to reduced G6PD activity, making red blood cells more susceptible to oxidative damage by certain substances (e.g., fava beans, certain medications) and causing hemolysis (destruction of red blood cells).

**Why Each Wrong Option is Incorrect:**

A. G6PD deficiency is a single gene disorder caused by mutations in the G6PD gene located on the X-chromosome. However, the deficiency results in reduced G6PD activity, causing oxidative stress and hemolysis, not a benign condition.

B. Although G6PD deficiency is caused by mutations on the X-chromosome, the correct answer does not mention the role of NADPH in preventing oxidative stress and detoxifying ROS.

C. G6PD deficiency is a common disorder in the Mediterranean region due to a high frequency of certain mutations like the "Mediterranean" mutation. However, option D states that it is a benign condition, which is incorrect.

E. While G6PD deficiency is a common disorder in the Mediterranean region, option D incorrectly states that it has no clinical consequences. In reality, G6PD deficiency can lead to hemolysis when exposed to fava beans or certain medications, causing acute hemolysis episodes.

**Clinical Pearl:** G6PD deficiency is a common X-linked genetic disorder affecting red blood cells. It results from mutations in the G6PD gene, causing reduced G6PD activity and increased susceptibility to oxidative stress and hemolysis. Acute hemolysis can occur when patients consume fava beans or certain medications, leading to severe anemia and other complications.