Sex-linked dominant
Sex-linked dominant is a rare way that a genetic 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 include:
- Autosomal dominant
Autosomal dominant
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Read Article Now Book Mark Article - Autosomal recessive
Autosomal recessive
Autosomal recessive is one of several ways that a genetic trait, disorder, or disease can be passed down through families. An autosomal recessive dis...
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Chromosome
Chromosomes are structures found in the center (nucleus) of cells that carry long pieces of DNA. DNA is the material that holds genes. It is the bu...
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Gene
A gene is a short piece of DNA. Genes tell the body how to build specific proteins. There are about 20,000 genes in each cell of the human body. T...
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Heredity and disease
Genetics is the study of heredity, the process of a parent passing certain genes to their children. A person's appearance -- height, hair color, ski...
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Inheritance
Genetics is the study of heredity, the process of a parent passing certain genes to their children. A person's appearance -- height, hair color, ski...
Read Article Now Book Mark Article - Sex-linked recessive
Sex-linked recessive
Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes. Dominant inheritance occur...
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Information
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.
Dominant inheritance occurs when a variant gene from one parent can cause a disease, even though a matching gene from the other parent is normal. The variant gene dominates the gene pair.
For an X-linked dominant disorder: If the father has the variant 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 variant X gene, half of all her children (daughters and sons) will inherit the trait.
For example, if there are four children (two boys and two girls) and the mother is affected (she has one variant X and has the disease) but the father does not have the variant 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
If there are four children (two boys and two girls) and the father is affected (he has one variant X gene and has the disease) but the mother is not affected, the expected odds are:
- Two girls will have the disease
- Two boys will not have the disease
These odds do not mean that the children who inherit the variant X gene will show severe symptoms of the disease. The chance of inheritance is new with each conception, so these expected odds may not be what actually occurs in a family. Some X-linked dominant disorders are so severe that males with the genetic disorder may die before birth. Therefore, there may be an increased rate of miscarriages in the family or fewer male children than expected.
Reviewed By
Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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