NCI Dictionary of Genetics Terms

20 results found for: G

gene: (jeen); The basic unit of heredity passed from parent to child. Genes are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells. They contain information for making specific proteins that lead to the expression of a particular physical characteristic or trait, such as hair color or eye color, or to a particular function in a cell.
genetic anticipation: (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 condition is passed from one generation to the next.
genetic counseling: (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.
genetic heterogeneity: (jeh-NEH-tik HEH-teh-roh-jeh-NEE-ih-tee); A term used to describe different genetic mechanisms that produce the same or similar phenotypes. There are two types of genetic heterogeneity: allelic heterogeneity and locus heterogeneity. Allelic heterogeneity occurs when different variants at a single gene locus cause the same or similar phenotypic expressions of a disease or condition. Locus heterogeneity occurs when variants at different gene loci cause the same or similar phenotypic expressions of a disease or condition.
genetic marker: (jeh-NEH-tik MAR-ker); A sequence of DNA with a known physical location on a chromosome. Genetic markers and genes that are close to each other on a chromosome tend to be inherited together. Genetic markers vary between individuals to the extent that they can be used to help find a nearby gene causing a certain disease or trait within a family. Examples of genetic markers are single polymorphism nucleotides (SNPs), restriction fragment length polymorphisms (RFLPs), variable number of tandem repeats (VNTRs), microsatellites, and copy number variants (CNVs). Genetic markers may or may not have a known function.
genetic predisposition: (jeh-NEH-tik PREE-dih-spuh-ZIH-shun); An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having a genetic predisposition does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic susceptibility, hereditary predisposition, and inherited predisposition.
genetic screening: (jeh-NEH-tik SKREE-ning); The process of testing individuals in a given population to identify those who have an increased risk of having or developing a particular genetic disorder or carrying a genetic variant for a particular disorder.
genetic susceptibility: (jeh-NEH-tik suh-SEP-tih-BIH-lih-tee); An increased chance or likelihood of developing a particular disease based on the presence of one or more genetic variants and/or a family history suggestive of an increased risk of the disease. Having a genetic susceptibility does not mean an individual will develop the disease. Lifestyle and environmental factors can also affect an individual's risk of disease. Also called genetic predisposition, hereditary predisposition, and inherited predisposition.
genodermatosis: (JEE-noh-DER-muh-TOH-sis); An inherited syndrome that includes a dermatological (skin) phenotype.
genome-wide association study: (JEE-nome ... uh-SOH-see-AY-shun STUH-dee); A method used to identify inherited genetic variants associated with risk for a particular disease or trait. A genome-wide association study looks at the entire genome for genetic variants, usually single nucleotide polymorphisms (SNPs), that tend to occur more often in individuals with the disease or trait being studied than in those without the disease or trait. Also called GWAS.
genomic imprinting: (jeh-NOH-mik im-PRIN-ting); An epigenetic process resulting in the inactivation of an allele depending on which parent it was inherited from. Genomic imprinting can have clinical relevance because it may affect the expression of a gene mutation (i.e., the phenotype) in the offspring of an affected parent depending on which parent is passing on the mutation.
genotype: (JEE-noh-tipe); A term that refers to the two alleles present at a specific locus in the genome. Genotype also refers to the entire genetic makeup of an individual.
genotyping: (JEE-noh-ty-ping); A laboratory process in which an individual’s germline DNA is analyzed for specific nucleotides or bases to determine whether certain variants are present. Genotyping differs from sequencing in which all of the nucleotides comprising a specific length of DNA are assessed (e.g., within a gene, exome, or genome).
germline: (JERM-line); The cells from which eggs or sperm (i.e., gametes) are derived.
germline DNA: (JERM-line ...); Germline DNA refers to tissue derived from reproductive cells (egg or sperm) that become incorporated into the DNA of every cell in the body of the offspring. A germline mutation may be passed from parent to offspring. Also called constitutional DNA.
germline mosaicism: (JERM-line moh-ZAY-ih-SIH-zum); A term that refers to the presence of a pathogenic variant that is confined to the ovaries or testes. Germline mosaicism occurs when some of the sperm cells in the testes or some of the egg cells in the ovaries carry a pathogenic variant that is not found in other cells of the body. This means that a parent may not develop a genetic condition but could pass it on to one or more of their children. Also called gonadal mosaicism.
germline mutation: (JERM-line myoo-TAY-shun); A mutation in a reproductive cell (egg or sperm) that is in the DNA of every cell in the offspring's body. A mutation contained within the germline can be passed from parent to offspring and is, therefore, hereditary. Also called germline variant.
germline variant: (JERM-line VAYR-ee-unt); A variant in a reproductive cell (egg or sperm) that is in the DNA of every cell in the offspring's body. A variant contained within the germline can be passed from parent to offspring and is, therefore, hereditary. Also called germline mutation.
gonadal mosaicism: (goh-NA-dul moh-ZAY-ih-SIH-zum); A term that refers to the presence of a pathogenic variant that is confined to the ovaries or testes. Gonadal mosaicism occurs when some of the sperm cells in the testes or some of the egg cells in the ovaries carry a pathogenic variant that is not found in other cells of the body. This means that a parent may not develop a genetic condition but could pass it on to one or more of their children. Also called germline mosaicism.
GWAS: A method used to identify inherited genetic variants associated with risk for a particular disease or trait. A GWAS looks at the entire genome for genetic variants, usually single nucleotide polymorphisms (SNPs), that tend to occur more often in individuals with the disease or trait being studied than in those without the disease or trait. Also called genome-wide association study.