On this page you will learn about how DMD is inherited. DMD is a genetic disease passed from one generation to the next in an X-linked recessive fashion. This means that females carry the defective gene that causes the disorder, but the disease almost exclusively affects males. When a mother carries the defective gene, her female children each have a 50 percent chance of carrying the gene also, but they, too, will not usually show any symptoms or may have only mild symptoms. However, each male child has a 50 percent chance of having the disease and showing signs of the disorder. The following explains how the disease is inherited. The defective gene lies on the X-chromosome. A male has only one X-chromosome and one Y-chromosome, while a female has two X-chromosomes. This means that if a male receives an X-chromosome with the defective gene, he will show symptoms of the disease. A female on the other hand, since she has two X-chromosomes, has a better chance of not exhibiting the effects. Suppose a female has one X-chromosome with the defective gene on it. Since the disease is X-linked recessive, she does not have the disease, but she still carries the defective gene. But, if she has two chromosomes with the defective gene, she will show symptoms of the disease. (MDA 1998) One very important thing to know about DMD is that it is not always inherited. Sometimes, mutations in genes occur without any mutation being present in the parents. (MDA 1998)