|A service of the U.S. National Library of Medicine®|
Reviewed January 2010
What is the Y chromosome?
The Y chromosome is one of the two sex chromosomes in humans (the other is the X chromosome). The sex chromosomes form one of the 23 pairs of human chromosomes in each cell. The Y chromosome spans more than 59 million building blocks of DNA (base pairs) and represents almost 2 percent of the total DNA in cells.
Each person normally has one pair of sex chromosomes in each cell. The Y chromosome is present in males, who have one X and one Y chromosome, while females have two X chromosomes.
Identifying genes on each chromosome is an active area of genetic research. Because researchers use different approaches to predict the number of genes on each chromosome, the estimated number of genes varies. The Y chromosome likely contains 50 to 60 genes that provide instructions for making proteins. Because only males have the Y chromosome, the genes on this chromosome tend to be involved in male sex determination and development. Sex is determined by the SRY gene, which is responsible for the development of a fetus into a male. Other genes on the Y chromosome are important for male fertility.
Many genes are unique to the Y chromosome, but genes in areas known as pseudoautosomal regions are present on both sex chromosomes. As a result, men and women each have two functional copies of these genes. Many genes in the pseudoautosomal regions are essential for normal development.
Genes on the Y chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.
How are changes in the Y chromosome related to health conditions?
Many genetic conditions are related to changes in particular genes on the Y chromosome. This list of disorders associated with genes on the Y chromosome provides links to additional information.
Changes in the structure or number of copies of a chromosome can also cause problems with health and development. The following chromosomal conditions are associated with such changes in the Y chromosome.
Is there a standard way to diagram the Y chromosome?
Geneticists use diagrams called ideograms as a standard representation for chromosomes. Ideograms show a chromosome's relative size and its banding pattern. A banding pattern is the characteristic pattern of dark and light bands that appears when a chromosome is stained with a chemical solution and then viewed under a microscope. These bands are used to describe the location of genes on each chromosome.
See How do geneticists indicate the location of a gene? in the Handbook.
Where can I find additional information about the Y chromosome?
You may find the following resources about the Y chromosome helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
Where can I find general information about chromosomes?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding the Y chromosome?
adolescent ; aneuploidy ; azoospermia ; cell ; chromosome ; DNA ; fertility ; fetus ; gene ; hormone ; infertility ; IQ ; mosaicism ; pseudoautosomal region ; sex chromosomes ; sex determination ; sperm ; spermatogenesis ; stature ; syndrome ; testes ; testosterone ; translocation
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (19 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.