The gene responsible for causing Duchenne muscular dystrophy is found on

The correct option is X chromosome.

Step-by-step Explanation:
1. Understanding Duchenne Muscular Dystrophy (DMD): Duchenne muscular dystrophy is a genetic disorder characterized by progressive muscle weakness and degeneration. It is caused by an absence of dystrophin, a protein that helps keep muscle cells intact.
2. The DMD Gene: The instructions for creating the dystrophin protein are carried by the DMD gene, which is one of the largest genes in the human genome.
3. Chromosomal Location: The DMD gene is located on the sex-determining X chromosome (specifically on the short arm at position Xp21.1).
4. X-linked Recessive Inheritance: Because the gene is located on the X chromosome, the condition is inherited in an X-linked recessive manner. Males have only one X chromosome (inherited from their mother), meaning a mutation in their single copy of the DMD gene is sufficient to cause the disease. Females, having two X chromosomes, must inherit two mutated copies of the gene to show symptoms, which is extremely rare; instead, they usually act as carriers if they possess one mutated copy.