How does inheritance work in X-linked recessive diseases?
X-linked diseases are those that come from gene defects on the X chromosome. These disorders affect males almost exclusively, because males have only one X chromosome. This means they have no “backup” copy of a normal gene on a second X chromosome. Females have two X chromosomes, so a gene defect on one of them usually doesn’t pose much of a problem. A normal gene on the female’s other X chromosome serves as a “backup” copy. A woman with an X-linked gene defect usually doesn’t show any signs of an X-linked disease. However, she’s a carrier of the disease and can pass it to her sons. Her sons each have a 50 percent chance of inheriting the abnormal gene and getting the disease. Her daughters each have a 50 percent chance of inheriting the gene and being carriers of the disorder. Spontaneous mutations in X-chromosome genes can lead to X- linked recessive diseases in boys. Are there tests that detect carriers of muscular dystrophy? Yes. MDA-supported researchers have developed accurate pr
