Question:medium
All of the following statements about the genetics of G6PD deficiency are true, EXCEPT:
All of the following statements about the genetics of G6PD deficiency are true, EXCEPT:
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Variable enzyme levels in carrier females actually prove, not disprove, random X-inactivation.
Updated On: Jun 24, 2026
- X-linked inheritance
- More severe in men
- Contradicts the Lyon hypothesis
- May affect heterozygous females
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: G6PD deficiency maps to band Xq28, making it an X-linked condition. Because males are hemizygous (one X only), an abnormal allele has no normal counterpart and the clinical effect is greater in males.
Step 2: The Lyon hypothesis states that random inactivation of one X chromosome occurs in every cell of a female. In a heterozygous woman this yields a mixture of roughly 50 percent normal and 50 percent enzyme-deficient red cells, so she may indeed manifest hemolysis to a variable degree.
Step 3: Far from contradicting Lyon, this variable mosaic expression in carrier females is a classic illustration of the Lyon hypothesis. The statement that G6PD deficiency contradicts the Lyon hypothesis is therefore incorrect.
Step 4: The exception we must pick is the claim that it contradicts Lyon's hypothesis.
\[\boxed{\text{Contradicts Lyon Hypothesis}}\]
Step 2: The Lyon hypothesis states that random inactivation of one X chromosome occurs in every cell of a female. In a heterozygous woman this yields a mixture of roughly 50 percent normal and 50 percent enzyme-deficient red cells, so she may indeed manifest hemolysis to a variable degree.
Step 3: Far from contradicting Lyon, this variable mosaic expression in carrier females is a classic illustration of the Lyon hypothesis. The statement that G6PD deficiency contradicts the Lyon hypothesis is therefore incorrect.
Step 4: The exception we must pick is the claim that it contradicts Lyon's hypothesis.
\[\boxed{\text{Contradicts Lyon Hypothesis}}\]
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