Duchennes pseudo muscular hypertrophy is inherited as –
First, the core concept here is X-linked recessive inheritance. Duchenne is a classic example of this. The gene involved is dystrophin on the X chromosome. Males are more affected because they have only one X chromosome. Females can be carriers but usually don't show symptoms unless they're hemizygous or have skewed X-inactivation.
The correct answer should be X-linked recessive. The user needs to explain why this is the case. The wrong options would likely be other inheritance patterns like autosomal dominant, autosomal recessive, or Y-linked. Each of these is incorrect because Duchenne doesn't fit their patterns. For example, autosomal dominant would mean affected parents pass it to 50% of offspring regardless of sex, but Duchenne is more common in males. Autosomal recessive would require two copies, which isn't the case here. Y-linked is impossible because females are carriers.
Clinical pearl: Remember that X-linked recessive disorders often affect males more, and female carriers can have some symptoms due to X-inactivation. The key is the X chromosome's role and the dystrophin gene defect leading to muscle degeneration.
Now, structuring the explanation with the required sections. Make sure each part is concise and covers the necessary points without being too technical. Also, check that the clinical pearl is high-yield and memorable for exams. Avoid any markdown formatting as per the user's instructions. Let me put it all together now.
**Core Concept**
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder caused by mutations in the *dystrophin* gene on the X chromosome. Males (hemizygous) are predominantly affected, while females are typically asymptomatic carriers due to X-inactivation.
**Why the Correct Answer is Right**
DMD follows X-linked recessive inheritance. The dystrophin gene is located on the Xp21.1 region. Males inherit the X chromosome from their mothers; if the X carries a defective dystrophin gene, they develop the disease. Females with one defective X allele are carriers and may show mild symptoms due to random X-inactivation. Affected males cannot pass the mutation to their sons but transmit it to all daughters, who become carriers.
**Why Each Wrong Option is Incorrect**
**Option A:** Autosomal dominant inheritance would require affected individuals to have a 50% chance of passing the mutation to offspring regardless of sex, which does not fit DMD's clinical pattern.
**Option B:** Autosomal recessive inheritance would require two defective alleles (one from each parent), but DMD occurs in males with only one X chromosome, making this unlikely.
**Option C:** Y-linked inheritance is impossible because DMD occurs in females as carriers and affects males only.
**Clinical Pearl / High-Yield Fact**
DMD presents in early childhood with progressive muscle weakness, Gowers’ sign, and pseudohypertrophy of calves. Female carriers may show elevated creatine kinase (CK) levels. Always suspect X-linked recessive inheritance in conditions affecting males more severely, with maternal transmission.
**Correct Answer: D. X-linked recessive