Duchenne muscular dystrophy is a genetic disorder that arises from a recessive X-linked allele. Why is this disorder almost aways restricted to males?

1 Answer
Sep 9, 2016

Duchenne Muscular Dystrophy (DMD) is transmitted from a carrier mother to her son. A female can be affected by the disease only when her carrier mother gets married to an affected male .

Explanation:

DMD is caused by X linked recessive gene. A male gets affected by the disease as there is only one X chromosome (hemizygous condition in males) and normal version of the gene is not available. In carrier females, single dose of the wrong gene can not cause any harm as the other X chromosome carries normal form of the gene.

When a gamete with X chromosome, containing the wrong version of the gene from mother, gets fertilised by Y containing sperm, the resulting son will be affected by the disease.

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Probability of birth of an affected girl child was very low as affected males died in very young age. Nowadays, the life expectancy of affected males are increasing. Thus, possibility of birth of an affected female could rise.