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.
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.