## **Core Concept**
Duchenne muscular dystrophy (DMD) is a genetic disorder characterized by progressive muscle degeneration and weakness. It is caused by an absence of dystrophin, a protein that helps keep muscle cells intact. The disorder is linked to mutations in the dystrophin gene.

## **Why the Correct Answer is Right**
The correct answer, , indicates that Duchenne muscular dystrophy is inherited in an X-linked recessive pattern. This means the gene responsible for the condition is located on the X chromosome. Males have one X and one Y chromosome (XY), and females have two X chromosomes (XX). Because males have only one X chromosome, a single mutation in the dystrophin gene on the X chromosome is enough to cause the disorder. Females, on the other hand, would need both X chromosomes to have the mutation to express the disorder, making it less common in females.

## **Why Each Wrong Option is Incorrect**
* **Option A:** - This option suggests an autosomal dominant pattern, which is incorrect for Duchenne muscular dystrophy. In an autosomal dominant pattern, only one copy of the mutated gene is needed to cause the condition, and it would affect both males and females equally.
* **Option B:** - This option suggests an autosomal recessive pattern, which also does not apply to Duchenne muscular dystrophy. In an autosomal recessive pattern, two copies of the mutated gene (one from each parent) are needed to cause the condition, and it would also affect both males and females equally.
* **Option D:** - This option suggests a Y-linked pattern, which is incorrect because Y-linked traits are passed from father to son and Duchenne muscular dystrophy does not follow this inheritance pattern.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that because Duchenne muscular dystrophy is X-linked recessive, it predominantly affects males. Females are usually carriers unless they are homozygous for the mutation, which is rare. Carrier females have a 50% chance of passing the mutated gene to each son, who would be affected, and to each daughter, who would typically be a carrier.

## **Correct Answer:** . X-linked recessive.