Sex-linked dominant is a rare way that a trait or disorder can be passed down through families. One abnormal gene on the X chromosome can cause a sex-linked dominant disease.
Related terms and topics:
Inheritance of a specific disease, condition, or trait depends on the type of chromosome that is 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 can cause a 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. That is because daughters always inherit their father's X chromosome. If the mother carries the abnormal X gene, half of all their children (daughters and sons) will inherit the disease tendency.
For example, if there are four children (two boys and two girls) and the mother is affected (she has one abnormal X and has the disease) but the father does not have the abnormal X gene, the expected odds are:
If there are four children (two boys and two girls) and the father is affected (he has one abnormal X and has the disease) but the mother is not, the expected odds are:
These odds do not mean that the children who inherit the abnormal X will show severe symptoms of the disease.
Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant
Fogel BL, Geschwind DH. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 40.
Stankiewicz P, Lupsik JR. Gene, genomic, and chromosomal disorders. In: Goldman L, Ausiello D, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 40.
Updated by: Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2015, A.D.A.M., Inc. Duplication for commercial use must be authorized in writing by ADAM Health Solutions.