The mode of inheritance of Duchenne muscular dystrophy is
The core concept here is X-linked recessive inheritance. DMD is caused by mutations in the dystrophin gene located on the Xp21.1 region. Dystrophin is a protein important for muscle cell integrity. Without it, muscle fibers become damaged and die, leading to progressive muscle weakness.
Looking at the options, the correct answer would be X-linked recessive. The other options would be autosomal dominant, autosomal recessive, or maybe another type. Let's see why the others are wrong. Autosomal dominant would mean that one copy is enough, but DMD is not like that. Autosomal recessive would require two copies, but since the gene is on the X chromosome, that's not the case. Y-linked is impossible here because the dystrophin gene isn't on the Y. Mitochondrial inheritance is also not applicable here because the gene isn't in mitochondrial DNA.
Clinical pearl: Remember that X-linked recessive disorders are more common in males. Female carriers can pass the gene to their sons, who would be affected, and daughters, who would be carriers. So, family history and genetic testing are important for diagnosis and counseling.
So the correct answer is X-linked recessive. The options given in the question might have letters like B or C for this answer. Let me check the original question again. The correct answer is listed as option C, but in the user's input, the correct answer is not specified. Wait, the user provided the correct answer as "C. X-linked recessive" but in the question, the options are labeled A to D. So I need to make sure that in the explanation, I correctly identify the option letters as per the original question. But since the user hasn't provided the actual options, I'll just refer to the correct answer as the X-linked recessive one. But in the example given earlier, the correct answer was "C. X-linked recessive", so in the explanation, I need to structure the sections accordingly.
**Core Concept**
Duchenne muscular dystrophy (DMD) is a classic example of an **X-linked recessive disorder**, caused by mutations in the **dystrophin** gene on the X chromosome. Males (hemizygous for the X chromosome) are predominantly affected, while females are typically asymptomatic carriers.
**Why the Correct Answer is Right**
DMD follows **X-linked recessive inheritance**. The dystrophin gene on Xp21.1 is responsible for producing a protein critical for muscle cell membrane stability. Males with a single defective allele (X^dY) manifest the disease, while females with one defective allele (X^DX^d) are carriers. Affected males inherit the mutated X chromosome from their carrier mothers. Females with two defective alleles (X^dX^d) are extremely rare and may exhibit mild symptoms due to skewed X