Iowa Institute of Human Genetics

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  • X

    X-linked recessive:

     An inheritance pattern for which the causative gene of the given disorder is located on the X chromosome. As males have only one X chromosome (hemizygous, XY), a single gene change on the X chromosome is enough to cause the disorder or trait. Since women have two X chromosomes it is uncommon for women to have X linked disorders, but not impossible. Carrier females may express mild symptoms of the trait due to differences in X-chromosome inactivation. Examples of such diseases are hemophilia and Duchenne muscular dystrophy.

    X-linked dominant:

    An inheritance pattern for which the causative gene of the given disorder is located on the X chromosome. The phenotype can be expressed by both males and females, and affected males tend to have more severe symptoms than affected females.

    XLD:

    See x-linked dominant

    XLR:

    See x-linked recessive