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NCI Dictionary of Genetics Terms


10 results found for: N



  • negative predictive value  listen  (NEH-guh-tiv preh-DIK-tiv VAL-yoo)
    The likelihood that an individual with a negative test result is truly unaffected and/or does not have the particular gene mutation in question. Also called NPV.

  • new mutation  listen  (noo myoo-TAY-shun)
    An alteration in a gene that is present for the first time in one family member as a result of a mutation in a germ cell (egg or sperm) of one of the parents, or a mutation that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation.

  • noncarrier  listen  (non-KAYR-ee-er)
    An individual who does not carry a mutation previously identified in his or her family.

  • nonpenetrance  listen  (non-PEH-neh-trunts)
    The state in which a genetic trait, although present in the appropriate genotype, fails to manifest itself in the phenotype (e.g., a woman with a BRCA1 mutation who lives to be elderly and never develops breast or ovarian cancer).

  • nonsense mutation  listen  (NON-sens myoo-TAY-shun)
    A mutation that alters the genetic code in a way that causes the premature termination of a protein. The altered protein may be partially or completely inactivated, resulting in a change or loss of protein function.

  • novel mutation  listen  (NAH-vel myoo-TAY-shun)
    A newly discovered, distinct gene alteration; NOT the same as new or de novo mutation.

  • NPV 
    The likelihood that an individual with a negative test result is truly unaffected and/or does not have the particular gene mutation in question. Also called negative predictive value.

  • nucleotide  listen  (NOO-klee-oh-tide)
    A molecule consisting of a nitrogen-containing base (adenine, guanine, thymine, or cytosine in DNA; adenine, guanine, uracil, or cytosine in RNA), a phosphate group, and a sugar (deoxyribose in DNA; ribose in RNA). DNA and RNA are polymers comprised of many nucleotides, strung together like beads in a necklace.

  • null allele  listen  (nul uh-LEEL)
    A mutation that results in either no gene product or the absence of function at the phenotypic level.

  • nutrigenomics  listen  (NOO-trih-jeh-NOH-mix)
    The study of the interaction of dietary and genetic factors and its effect on metabolism, health status, and risk of disease.