Which forms of muscular dystrophy are X-linked? a. Becker b. Duchenne c. Facioscapulohumeral d. A combination of Becker and Duchenne"

The correct answers a and b.

The inheritance of Becker and Duchenne dystrophies are linked to the X chromosome.

Explanation:

Duchenne and Becker muscular dystrophies (DMD and BMD, respectively) are neuromuscular diseases characterized by progressive muscle atrophy and weakness, as a consequence of the degeneration of skeletal, smooth and cardiac muscles. Both muscular dystrophies are caused by mutations in the DMD gene, located on the X chromosome. This is the largest known human gene and it encodes a protein called dystrophin, which is expressed in muscle cells. The mutations responsible for DMD lead to a total absence of dystrophin, while those underlying DMB lead to an abnormal quantity and / or quality of the protein. In both cases it is common to find deletions of the gene.