X-Linked Inheritance

Genes are the blueprints for making the substances, called proteins, 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 basic patterns of inheritance of our genes is called X-linked inheritance.

What is X-linked inheritance?

X-linked inheritance means that the gene alteration causing the trait or the disorder is located on the X chromosome. Remember, females have two X chromosomes, while males have one X and one Y. Mutations in X chromosome genes 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. In general, X-linked recessive mutations are expressed in females only if a female has two copies of the mutation (one on each X chromosome). However, for males, if their only copy of the X chromosome contains a mutation, 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.

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