What is required for an individual to have a sex-linked disorder?

For an individual to have a sex-linked disorder, they must have a mutation in a gene located on one of the sex chromosomes, either the X or Y chromosome. These disorders are inherited in different patterns depending on the location of the mutated gene.

X-linked disorders:

X-linked disorders are caused by mutations in genes located on the X chromosome. These disorders primarily affect males because males only have one X chromosome. If a male inherits an X chromosome with a mutated gene, he will usually develop the disorder. Females have two X chromosomes, and in most cases, if they inherit one X chromosome with a mutated gene, the other X chromosome can compensate for the mutated gene, preventing the development of the disorder. However, females can carry these mutations and transmit them to their children. Common X-linked disorders include hemophilia, red-green color blindness, and Duchenne muscular dystrophy.

Y-linked disorders:

In contrast, Y-linked disorders are quite rare due to the limited number of genes present on the Y chromosome. Males are the only ones affected by Y-linked disorders because they are the only ones who have a Y chromosome. These disorders are passed down from father to son. Since genes on the Y chromosome are not involved in determining sex, females do not inherit or develop Y-linked disorders. There are few known Y-linked disorders, such as hypertrichosis pinnae, where males experience excessive hair growth in their external ear canals.

In summary, for an individual to have a sex-linked disorder, they must have a mutation in a gene located on either the X or Y chromosome. The inheritance pattern and expression of the disorder depend on the specific sex chromosome affected.