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Sex-linked dominant

Contents of this page:

Illustrations

Genetics
Genetics

Alternative Names    Return to top

Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant

Definition    Return to top

Sex-linked dominant is a rare way that a trait or disorder can be passed down through families. A single abnormal gene on the X chromosome can cause a sex-linked dominant disease.

Related terms and topics:

Information    Return to top

Inheritance of a specific disease, condition, or trait depends on the type of chromosome affected (autosomal or sex chromosome). It also depends on whether the trait is dominant or recessive. Sex-linked diseases are inherited through one of the sex chromosomes (the X or Y chromosome).

Dominant inheritance occurs when an abnormal gene from one parent is capable of causing disease, even though a matching gene from the other parent is normal. The abnormal gene dominates the gene pair.

For an X-linked dominant disorder: If the father carries the abnormal X gene, all of his daughters will inherit the disease and none of his sons will have the disease. If the mother carries the abnormal X gene, half of all their children (daughters and sons) will inherit the disease tendency.

In other words, if there are four children (two males and two females) and the mother is affected (one abnormal X, she has the disease) but the father is not, the statistical expectation is for:

If there are four children (two males and two females) and the father is affected (abnormal X, he has the disease) but the mother is not, the statistical expectation is for:

This does not mean that the children will necessarily be affected.

Update Date: 5/20/2008

Updated by: Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the American Board of Genetic Counseling, University of Tennessee, Memphis, TN. Review provided by VeriMed HealthcareNetwork. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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