NCI Dictionary of Genetics Terms

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The NCI Dictionary of Genetics Terms contains technical definitions for more than 200 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.

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16 results found for: N
negative predictive value
(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
(noo myoo-TAY-shun)
A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation, de novo variant, and new variant.
new variant
(noo VAYR-ee-unt)
A genetic alteration that is present for the first time in one family member as a result of a variant (or mutation) in a germ cell (egg or sperm) of one of the parents, or a variant that arises in the fertilized egg itself during early embryogenesis. Also called de novo mutation, de novo variant, and new mutation.
next-generation sequencing
(... JEH-neh-RAY-shun SEE-kwen-sing)
A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel. Also called massively parallel sequencing and NGS.
NGS
A high-throughput method used to determine a portion of the nucleotide sequence of an individual’s genome. This technique utilizes DNA sequencing technologies that are capable of processing multiple DNA sequences in parallel. Also called massively parallel sequencing and next-generation sequencing.
noncarrier
(non-KAYR-ee-er)
An individual who does not carry a mutation previously identified in his or her family.
noninferiority study
(non-in-FEER-ee-OR-ih-tee STUH-dee)
A research study that is designed to determine whether one intervention is not worse than another control intervention by a predetermined margin. An intervention that yields outcomes which are equivalent to or better than the control intervention is considered not inferior to the control intervention. Noninferiority studies are often conducted to examine whether a new, experimental treatment is not worse than an established standard of care.
nonpenetrance
(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
(NON-sens myoo-TAY-shun)
A genetic alteration 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. Also called nonsense variant.
nonsense variant
(NON-sens VAYR-ee-unt)
A genetic alteration 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. Also called nonsense mutation.
novel mutation
(NAH-vel myoo-TAY-shun)
A newly discovered, distinct genetic alteration; NOT the same as new or de novo variant (or mutation). Also called novel variant.
novel variant
(NAH-vel VAYR-ee-unt)
A newly discovered, distinct genetic alteration; NOT the same as new or de novo variant (or mutation). Also called novel 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
(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
(nul uh-LEEL)
A mutation that results in either no gene product or the absence of function at the phenotypic level.
nutrigenomics
(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.