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NCI Dictionary of Genetics Terms

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Welcome to the NCI Dictionary of Genetics Terms, which contains technical definitions for more than 150 terms related to genetics. These definitions were developed by the PDQ® Cancer Genetics Editorial Board to support the evidence-based, peer-reviewed PDQ cancer genetics information summaries.

Tips on Looking Up a Word or Phrase

  • In the search box, type the word or part of the word you are looking for and click the "Go" button.
  • Change the search from “Starts with” to “Contains” to find all terms in the dictionary that include a word or set of letters. For example, type “mutation” to find “de novo mutation” and “deleterious mutation”.
  • You can also click on a letter of the alphabet to browse through the dictionary or “All” to view it in its entirety.
  • The search box has an autosuggest feature. When you type three or more letters, a list of up to 10 suggestions will pop up below the box. Choose one of the suggestions or type more letters to find the term you want.
  • Additional genetics terms and definitions are available in the Talking Glossary of Genetics Terms on the National Human Genome Research Institute’s website. Many terms in the Talking Glossary of Genetics Terms are accompanied by illustrations, animations, and descriptions by specialists in the field of genetics.