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NCI Dictionary of Genetics Terms

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14 results found for: G



  • gene  listen  (jeen)
    The basic unit of heredity that occupies a specific location on a chromosome. Each consists of nucleotides arranged in a linear manner. Most genes code for a specific protein or segment of protein leading to a particular characteristic or function.

  • genetic anticipation  listen  (jeh-NEH-tik an-TIH-sih-PAY-shun)
    A phenomenon in which the signs and symptoms of some genetic conditions tend to become more severe and/or appear at an earlier age as the disorder is passed from one generation to the next. Huntington disease is an example of a genetic disorder in which the biological mechanism for this phenomenon has been well documented. In other cases, it may be due to factors such as increased surveillance or other nongenetic causes.

  • genetic counseling  listen  (jeh-NEH-tik KOWN-suh-ling)
    A communication process that seeks to assist affected or at-risk individuals and families in understanding the natural history, disease risks, and mode of transmission of a genetic disorder; to facilitate informed consent for genetic testing when appropriate; to discuss options for risk management and family planning; and to provide for or refer individuals for psychosocial support as needed. The National Society of Genetic Counselors Task Force has also defined the term genetic counseling.

  • genetic heterogeneity  listen  (jeh-NEH-tik HEH-teh-roh-jeh-NEE-ih-tee)
    The production of the same or similar phenotypes (observed biochemical, physiological, and morphological characteristics of a person determined by his/her genotype) by different genetic mechanisms. There are two types: (1) allelic heterogeneity – when different alleles at a locus can produce variable expression of a condition; and (2) locus heterogeneity – the term used to describe disease in which mutations at different loci can produce the same disease phenotype.

  • genetic marker  listen  (jeh-NEH-tik MAR-ker)
    An identifiable segment of DNA (e.g., Single Nucleotide Polymorphism [SNP], Restriction Fragment Length Polymorphism [RFLP], Variable Number of Tandem Repeats [VNTR], microsatellite) with enough variation between individuals that its inheritance and co-inheritance with alleles of a given gene can be traced; used in linkage analysis.

  • genetic predisposition  listen  (jeh-NEH-tik PREE-dih-spuh-ZIH-shun)
    Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic susceptibility.

  • genetic screening  listen  (jeh-NEH-tik SKREE-ning)
    Genetic testing designed to identify individuals in a given population who are at higher risk of having or developing a particular disorder, or carrying a gene for a particular disorder.

  • genetic susceptibility  listen  (jeh-NEH-tik suh-SEP-tih-BIH-lih-tee)
    Increased likelihood or chance of developing a particular disease due to the presence of one or more gene mutations and/or a family history that indicates an increased risk of the disease. Also called genetic predisposition.

  • genodermatosis  listen  (JEE-noh-DER-muh-TOH-sis)
    An inherited syndrome that includes a dermatological (skin) phenotype.

  • genome-wide association study  listen  (JEE-nome ... uh-SOH-see-AY-shun STUH-dee)
    Genome-wide association studies (GWAS) are a way for scientists to identify genes involved in human disease. This method searches the genome for small variations, called single nucleotide polymorphisms or SNPs (pronounced “snips”), that occur more frequently in people with a particular disease than in people without the disease. Also called GWAS, WGA study, and whole genome association study.

  • genomic imprinting  listen  (jeh-NOH-mik im-PRIN-ting)
    The process by which one chromosome of a pair is chemically modified, depending on whether the chromosome comes from the father or the mother. These modifications lead to differential expression of a gene or genes on a maternally derived chromosome versus a paternally derived chromosome.

  • genotype  listen  (JEE-noh-tipe)
    At its broadest level, genotype includes the entire genetic constitution of an individual. It is often applied more narrowly to the set of alleles present at one or more specific loci.

  • germline  listen  (JERM-line)
    The cells from which eggs or sperm (i.e., gametes) are derived.

  • GWAS  listen
    GWAS (genome-wide association studies) are a way for scientists to identify genes involved in human disease. This method searches the genome for small variations, called single nucleotide polymorphisms or SNPs (pronounced “snips”), that occur more frequently in people with a particular disease than in people without the disease. Also called genome-wide association study, WGA study, and whole genome association study.