NCI Dictionary of Genetics Terms
15 results found for: G
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.
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.
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 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.
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.
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 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.
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.
An inherited syndrome that includes a dermatological (skin) phenotype.
genome-wide association study
(JEE-nome ... uh-SOH-see-AY-shun STUH-dee)
A genome-wide association study (GWAS) is a way for scientists to identify inherited genetic variants associated with risk of disease or a particular trait. This method surveys the entire genome for genetic polymorphisms, typically single nucleotide polymorphisms (SNPs) (pronounced “snips”), that occur more frequently in cases (people with the disease or trait being assessed) than in controls (people without the disease or trait). Also called GWAS.
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.
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.
The cells from which eggs or sperm (i.e., gametes) are derived.
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.
A GWAS (genome-wide association study) is a way for scientists to identify inherited genetic variants associated with risk of disease or a particular trait. This method surveys the entire genome for genetic polymorphisms, typically single nucleotide polymorphisms (SNPs) (pronounced “snips”), that occur more frequently in cases (people with the disease or trait being assessed) than in controls (people without the disease or trait). Also called genome-wide association study.