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Reviewed April 2010
What is chromosome 20?
Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Two copies of chromosome 20, one copy inherited from each parent, form one of the pairs. Chromosome 20 spans about 63 million DNA building blocks (base pairs) and represents approximately 2 percent of the total DNA in cells.
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. Chromosome 20 likely contains 500 to 600 genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.
Genes on chromosome 20 are among the estimated 20,000 to 25,000 total genes in the human genome.
How are changes in chromosome 20 related to health conditions?
Many genetic conditions are related to changes in particular genes on chromosome 20. This list of disorders associated with genes on chromosome 20 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 chromosome 20.
Is there a standard way to diagram chromosome 20?
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 chromosome 20?
You may find the following resources about chromosome 20 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 chromosome 20?
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (16 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.