NCI Dictionary of Genetics Terms

11 results found for: L

late or variable onset: (layt … VAYR-ee-uh-bul …); Refers to the age at which a disease phenotype is expressed in an individual who carries a pathogenic variant. Conditions with late or variable onset generally manifest later in life or at no fixed time over the course of a lifetime.
LD: Where alleles (DNA markers) occur together more often than can be accounted for by chance because of their physical proximity on a chromosome. Also called linkage disequilibrium.
linkage: (LING-kij); The tendency for genes or other segments of DNA to be inherited together during meiosis because of their location near one another on the same chromosome. Finding linked genes can help identify a disease-causing gene.
linkage analysis: (LING-kij uh-NA-lih-sis); A gene-hunting technique that traces patterns of disease in high-risk families. Linkage analysis attempts to locate a disease-causing gene by identifying genetic markers of known chromosomal location that are co-inherited with the gene or trait of interest.
linkage disequilibrium: (LING-kij dis-EE-kwih-LIH-bree-um); Where alleles (DNA markers) occur together more often than can be accounted for by chance because of their physical proximity on a chromosome. Also called LD.
locus: (LOH-kus); The physical location of a specific gene on a chromosome.
locus heterogeneity: (LOH-kus HEH-teh-roh-jeh-NEE-ih-tee); The presence of variants at different gene loci that cause the same or similar phenotypic expressions of a disease or condition.
LOD score: (… skor); A statistical estimate of whether two genetic loci are physically near enough to each other (or "linked") on a particular chromosome that they are likely to be inherited together. A LOD score of 3 or higher is generally understood to mean that two genes are located close to each other on the chromosome. In terms of significance, a LOD score of 3 means the odds are 1,000:1 that the two genes are linked and therefore inherited together. Also called logarithm of the odds score.
logarithm of the odds score: (LAW-guh-RIH-thum … skor); A statistical estimate of whether two genetic loci are physically near enough to each other (or "linked") on a particular chromosome that they are likely to be inherited together. A logarithm of the odds score of 3 or higher is generally understood to mean that two genes are located close to each other on the chromosome. In terms of significance, a logarithm of the odds score of 3 means the odds are 1,000:1 that the two genes are linked and therefore inherited together. Also called LOD score.
LOH: If there is one normal and one abnormal allele at a particular locus, as might be seen in an inherited autosomal dominant cancer susceptibility disorder, loss of the normal allele produces a locus with no normal function. When the loss of heterozygosity involves the normal allele, it creates a cell that is more likely to show malignant growth if the altered gene is a tumor suppressor gene. Also called loss of heterozygosity.
loss of heterozygosity: (… HEH-teh-roh-zy-GAH-sih-tee); If there is one normal and one abnormal allele at a particular locus, as might be seen in an inherited autosomal dominant cancer susceptibility disorder, loss of the normal allele produces a locus with no normal function. When the loss of heterozygosity involves the normal allele, it creates a cell that is more likely to show malignant growth if the altered gene is a tumor suppressor gene. Also called LOH.