About Genetics Home Reference

Genetics Home Reference is a service of the U.S. National Library of Medicine, part of the National Institutes of Health, an agency of the Department of Health and Human Services.

There is no advertising on this site, nor does Genetics Home Reference endorse any company or product.

Condition Summaries

Each summary describes the major features of the condition, provides information about the condition's genetic basis, and explains its pattern of inheritance. The summaries also link to support organizations and additional information about the condition.

Gene Summaries

Each summary provides the official name and symbol of a gene, its chromosomal location, an explanation of its normal function, and the health implications of variations in the gene. Each gene summary links to more detailed information about the gene.

Chromosome Summaries

Chromosome summaries provide an estimate of the amount of DNA and number of genes for each chromosome and for mitochondrial DNA. Chromosomal conditions link directly to related chromosomes, with an explanation of how changes in the number or structure of chromosomes can lead to certain disorders.

Handbook

Help Me Understand Genetics Handbook is an illustrated, basic explanation of how genes work and how mutations cause disorders. It also includes current information about genetic testing, gene therapy, and the Human Genome Project.

Glossary

A glossary of genetic and medical terms is available from every web page. In addition, each summary provides a list of glossary terms used on the page, with a direct link to their definitions.

The main health topics in MedlinePlus® that have a genetic component are selected for inclusion in Genetics Home Reference. Conditions are chosen based on whether they have a known genetic basis. If your topic of interest is not yet included, please check back regularly for new information.

Genetics Home Reference is developed by a Staff that includes board-certified medical geneticists, biologists, and computer and information scientists. The content is reviewed regularly to ensure that it is accurate and up-to-date. External Expert Reviewers perform a comprehensive review of each condition and gene summary before it is posted to Genetics Home Reference and every one to two years thereafter. The date of the last comprehensive review is noted at the bottom of each summary.

Genetics Home Reference provides access to information from the National Library of Medicine, the National Institutes of Health, and other U.S. Government agencies.

To complement U.S. Government sources, Genetics Home Reference links to selected nonfederal web sites, consistent with Selection Criteria for Web Links. The links do not constitute an endorsement. We are not responsible for the content of those web sites.

An icon () signals that a link leaves Genetics Home Reference.

Before seeking medical or health information on the web, consumers may review the MedlinePlus® topic on Evaluating Health Information.

Genetics Home Reference is a starting point for consumers interested in learning about human genetics and inherited disorders. We strive to make sure that this information is current and accurate.

Scientists around the world are continually learning more about human genetics through research studies. Some of these studies produce conflicting or unexpected results that only future research will resolve. Genetics Home Reference usually excludes controversial or unproven information until it is clarified by additional studies.

Each condition, gene, and chromosome summary on Genetics Home Reference includes a date of last review near the top of the page. This date indicates when the content of that page was researched and updated by our staff.

As new data emerge from genetics research, Genetics Home Reference staff relies on some basic guidelines to determine what information to include on the web site:

• To include a specific genetic condition, it must be associated with defined genetic variations such as gene mutations or chromosomal changes.
• To include a particular gene with a genetic condition, genetic variations must have been identified in two or more unrelated individuals or families.
• In most cases, data must be available from human studies whose results have been confirmed by other research (replicated). Research findings are usually excluded if they come from studies done only with animals or with populations of human cells that have been maintained artificially for long periods of time (cell lines).

Every condition, gene, and chromosome summary in Genetics Home Reference links to PubMed®, a service of the National Library of Medicine. Each of these links leads to a list of relevant articles from the biomedical literature. In addition, a link to references, located at the end of each summary, lists the scientific articles used to develop the content for that summary.

For more technical information, each gene and chromosome summary provides links to resources that are designed for genetics professionals and researchers. These resources include in-depth information about gene and chromosome structure, function, and variation. Additional links to cutting-edge research information can be found in the Resources for Genetic Researchers.

Genetics Home Reference indexes many topics under more than one name, especially when the same topic may be known by different scientific, informal, and historical names.

The main heading for each topic reflects recent research and guidance from experts in the field of medical genetics.

Gene names and symbols are standardized: Genetics Home Reference uses gene terminology from Entrez Gene at the National Center for Biotechnology Information.

For more information about how genetic conditions and genes often get their names, see How are genetic conditions and genes named? in the Handbook.

Genetics Home Reference provides a printable version of the entire Handbook, complete with illustrations. Choose Printable PDF on the Handbook page to access this version. You must have a PDF reader installed on your computer to read and print this type of file. The Handbook is not available in a pre-printed or booklet form at this time.

You may copy and use illustrations and other content from Genetics Home Reference in accordance with the Terms and Conditions of Use. When crediting Genetics Home Reference as the source, you may follow the example in Citing the Genetics Home Reference.

Sometimes Genetics Home Reference illustrations are requested at higher resolution for use in other publications. These illustrations are created for the web, and unfortunately, high resolution versions are not available.

The What's New page always lists the latest topics on Genetics Home Reference. You can also Subscribe for Updates from Genetics Home Reference to receive announcements by email or RSS.

If you have questions or comments regarding Genetics Home Reference, please contact NLM Customer Service.