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NCI Dictionary of Genetics Terms

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NCI Dictionary of Genetics Terms


8 results found for: I



  • inconclusive  (IN-kun-KLOO-siv)
    A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called indeterminate and uninformative.

  • indeterminate  (IN-deh-TER-mih-nut)
    A negative test result in an individual where a clearly deleterious mutation has not been found in any family members. The genetic risk status of such an individual must be interpreted in the context of his or her personal and family history. Also called inconclusive and uninformative.

  • index case  (IN-dex kays)
    A clinically affected individual through whom attention is first drawn to a genetic disorder in a family.

  • informative  (in-FOR-muh-tiv)
    In genetic testing, a test result that reveals definitively the presence or absence of the germline genetic alteration associated with the hereditary disorder being assessed. In linkage analysis, the ability to distinguish between maternally inherited and paternally inherited DNA markers (polymorphisms) within or near a given gene of interest.

  • informed consent  listen  (in-FORMD kun-SENT)
    A process of information exchange between a clinician and an individual or their legal proxy designed to facilitate autonomous, informed decision making. The informed consent process for genetic testing should include an explanation of the medical and psychosocial risks, benefits, limitations, and potential implications of genetic analysis, a discussion of privacy, confidentiality, the documentation and handling of genetic test results, as well as options for managing the hereditary disease risk. Also called consent process.

  • inherited cancer syndrome  (in-HAYR-ih-ted KAN-ser SIN-drome)
    Describes the clinical manifestations associated with a mutation conferring cancer susceptibility.

  • intron  (IN-tron)
    The sequence of DNA in between exons that is initially copied into RNA but is cut out of the final RNA transcript and therefore does not change the amino acid code. Some intronic sequences are known to affect gene expression.

  • inversion  (in-VER-zhun)
    A chromosomal defect in which a segment of the chromosome breaks off and reattaches in the reverse direction.