Sex-linked dominant

Genetics

Genetics is the study of heredity and how traits are passed along from parents to offspring. Genes are contained within the chromosomes found within the egg and sperm. Each parent contributes one half of each pair or 23 chromosomes to their child, 22 autosomal and 1 sex chromosome. The inheritance of genetic diseases, abnormalities, or traits is described by both the type of chromosome the abnormal gene resides on (autosomal or sex chromosome), and by whether the gene itself is dominant or recessive.

Also known as: Inheritance - sex-linked dominant, Genetics - sex-linked dominant, X-linked dominant or Y-linked dominant

Definition

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

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:

  • Two children (one girl and one boy) with the disease
  • Two children (one girl and one boy) without the disease

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:

  • Two girls with the disease
  • Two boys without the disease

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

See also:

  • Special Topic

    Autosomal recessive

    Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal must be present in order for the disease or trait to develop.

  • Special Topic

    Chromosome

    Chromosomes and DNA

    Chromosomes are long pieces of DNA found in the center (nucleus) of cells. DNA is the material that holds . It is considered the building block of the human body.

  • Special Topic

    Autosomal dominant

    Autosomal dominant genes

    Autosomal dominant is one of several ways that a trait or disorder can be passed down through families. If a disease is autosomal dominant, it means you only need to get the abnormal from one parent in order for you to inherit the disease. One of the parents may often have the disease.

  • Special Topic

    Genetic counseling

    Genetic counseling and prenatal diagnosis

    Genetic counseling is a process in which a qualified professional shares information about genetic conditions. This information includes specifics about the condition in question, tests used to identify that condition, and help in understanding any laboratory test results. This helps parents, ...

  • Special Topic

    Genes

    A gene is a short piece of DNA, which tells the body how to build a specific . There are approximately 30,000 genes in each cell of the human body. The combination of all genes makes up the blueprint for the human body and its functions. A person’s genetic makeup is called a genotype.

  • Special Topic

    Genetics

    Genetics

    Genetics is the study of heredity, the process in which a parent passes certain onto their children. A person’s appearance — height, hair color, skin color, and eye color — are determined by genes. Other characteristics affected by heredity: Likelihood of getting certain ...

  • Special Topic

    Sex-linked recessive

    Genetics

    Sex-linked diseases are inherited through one of the “sex chromosomes” — the X or Y chromosomes. Autosomally inherited diseases are inherited through the non-sex chromosomes (autosomes), pairs 1 through 22. Dominant inheritance occurs when an abnormal gene from one parent is able ...

Review date:
April 26, 2010
Reviewed by:
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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