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X-linked Inheritance

Genes are the blueprints for making proteins, the�substances our bodies need to develop and work properly. Most genes come in pairs, one of which is inherited from the mother and the other from the father. A mutation is a change in a gene that prevents it from working properly. Mutations in genes are inherited from our biological parents in specific ways. One of the�common patterns of genetic inheritance is called X-linked inheritance.

What is X-linked inheritance?

X-linked inheritance means that the gene change (alteration or mutation) causing the trait or the disorder is located on the X chromosome. Remember, females have�2 X chromosomes, while males have�1 X and�1 Y chromosome. Mutations in genes on the�X chromosome can be recessive or dominant. Their expression in females and males is not the same because the genes on the Y chromosome do not exactly pair up with the genes on the X chromosome. In general, X-linked recessive mutations are expressed in females only�when they have�2 copies of the mutation (1 on each X chromosome). However, for males, if their only copy of the X chromosome contains a genetic mutation, then they will have the trait or disorder. To date, no cancer susceptibility genes have been identified on the X chromosome. However, research studies of families with a strong history of prostate cancer have found evidence that there might be a prostate cancer susceptibility gene on this chromosome.