G-6-PD deficiency is inherited as?
First, the core concept here is the inheritance pattern of genetic disorders. G-6-PD stands for glucose-6-phosphate dehydrogenase. I think this enzyme is located in red blood cells, and the deficiency leads to hemolysis when there's oxidative stress. Since it's an X-linked condition, males are more commonly affected because they have only one X chromosome. Females, having two Xs, are usually carriers unless they have two defective copies.
Now, the correct answer should be X-linked recessive. Let me check why. The gene for G-6-PD is on the X chromosome. Males (XY) need only one defective allele to show the condition, while females (XX) need two. This explains why males are more frequently affected.
Looking at the wrong options: if an option says autosomal recessive, that's incorrect because the gene isn't on an autosome. Autosomal dominant would mean each child has a 50% chance if one parent is affected, but that's not the case here. X-linked dominant is another possibility, but in that case, females would show the condition with one defective X, and males would show it if they have the one X with the mutation. However, X-linked recessive is more common for G-6-PD.
Clinical pearl: Remember that X-linked recessive disorders like G-6-PD deficiency present more in males. Also, females can be carriers and sometimes show symptoms if there's skewed X-inactivation. So, when a question mentions a male predominance in an enzyme deficiency, think X-linked recessive.
So the correct answer is X-linked recessive. The options that are autosomal or dominant are wrong because they don't fit the gene's location on the X chromosome. The X-linked dominant is incorrect because the inheritance pattern isn't consistent with that.
**Core Concept**
G-6-PD deficiency is an X-linked recessive disorder caused by mutations in the *G6PD* gene on the X chromosome. Males (hemizygous) are more commonly affected, while females (heterozygous) are typically asymptomatic carriers.
**Why the Correct Answer is Right**
The *G6PD* gene is located on the X chromosome. Males inherit their single X chromosome from their mother; if defective, they express the deficiency. Females require two defective X alleles (one from each parent) to manifest the condition. This X-linked recessive pattern explains the male predominance in clinical cases.
**Why Each Wrong Option is Incorrect**
**Option A:** *Autosomal dominant* is incorrect because the gene is not on an autosome, and dominant inheritance would require only one defective allele for females to express the condition.
**Option B:** *Autosomal recessive* is incorrect because the gene location is X-linked, not autosomal.
**Option D:** *X-linked dominant* is incorrect because dominant X-linked inheritance would result in affected females with a single defective X allele, which is not typical for G-6-PD deficiency.
**Clinical Pearl