Sex-linked dominant: MedlinePlus Medical Encyclopedia

P 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.
P Related terms and topics include:
- Autosomal dominant
- Autosomal recessive
- Chromosome
- Gene
- Heredity and disease
- Inheritance
- Sex-linked recessive

T Information
P Inheritance of a specific disease, condition, or trait depends on the type of chromosome that is affected. It can be either an autosomal chromosome or a sex chromosome. It also depends on whether the trait is dominant or recessive. Sex-linked diseases are inherited through one of the sex chromosomes, which are the X and Y chromosomes.
P 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.
P 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.
P 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:
- Two children (one girl and one boy) will have the disease
- Two children (one girl and one boy) will not have the disease
P 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:
- Two girls will have the disease
- Two boys will not have the disease
P These odds do not mean that the children who inherit the abnormal X will show severe symptoms of the disease.

T Alternative Names
P Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant

T Images
- Genetics

T References
P Feero WG, Zazove P, Chen F. Clinical genomics. In: Rakel RE, Rakel D, eds. Textbook of Family Medicine. 9th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 43.
P Groden J, Gocha AS, Croce CM. Human basic genetics and patterns of inheritance. In: Creasy RK, Resnik R, Iams JD, Lockwood CJ, Moore TR, Greene MF, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 7th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 1.
P Korf BR. Principles of genetics. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 40.

T Review Date 1/25/2016
P Updated by: Chad Haldeman-Englert, MD, FACMG, Fullerton Genetics Center, Asheville, 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.

