**Core Concept:** X-linked inheritance is a mode of genetic transmission where the gene for a trait is located on the X chromosome. In males, one X chromosome is present while females have two X chromosomes. Males are more likely to express the disease phenotype due to the single X chromosome.

**Why the Correct Answer is Right:** Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder caused by mutations in the dystrophin gene. Dystrophin is a protein that helps maintain the structural integrity of muscle cells, and its absence leads to progressive muscle weakness and wasting.

**Why Each Wrong Option is Incorrect:**

A. Hemophilia A and B (factor VIII and IX deficiency) are also X-linked disorders, but they are caused by mutations in the clotting factor genes and affect the blood clotting process, not muscle function.

B. Cystic Fibrosis is caused by mutations in the CFTR gene and affects the respiratory, digestive, and reproductive systems due to impaired chloride transport. It is not related to muscle function.

C. Tay-Sachs disease, caused by mutations in the HEXA gene, is an autosomal recessive disorder affecting the nervous system and is unrelated to muscle function.

**Clinical Pearl:** Understanding the mode of inheritance for different diseases is crucial in diagnosing and counselling patients and their families. Inheritance patterns help determine the sex of the affected individual and the risk for relatives.

**Correct Answer:** Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder affecting muscle function.