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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9 results found for: H
haploinsufficiency
(HA-ploh-IN-suh-FIH-shen-see)
The situation that occurs when one copy of a gene is inactivated or deleted and the remaining functional copy of the gene is not adequate to produce the needed gene product to preserve normal function.
haplotype
(HA-ploh-tipe)
A set of closely linked genetic markers present on one chromosome which tend to be inherited together.
hemizygous
(HEH-mee-ZY-gus)
Describes an individual who has only one member of a chromosome pair or chromosome segment rather than the usual two. Hemizygosity is often used to describe X-linked genes in males who have only one X chromosome. This term is sometimes used in somatic cell genetics where cancer cell lines are often hemizygous for certain alleles or chromosomal regions.
heritability
(HAYR-ih-tuh-BIH-lih-tee)
The proportion of variation in a population trait that can be attributed to inherited genetic factors. Heritability estimates range from 0 to 1 and are often expressed as a percentage. A number close to 1 may be indicative of a highly heritable trait within a population. It should not be used to estimate risk on an individual basis.
heteroduplex analysis
(HEH-teh-roh-DOO-plex uh-NA-lih-sis)
A method of detecting sequence differences between normal DNA and the DNA to be tested. It is commonly used as a screening method to detect potential mutations in a gene.
heterogeneity logarithm of the odds score
(HEH-teh-roh-jeh-NEE-ih-tee 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 heterogeneity logarithm of the odds score is calculated in the presence of locus heterogeneity (when the same phenotype can be caused by mutations in genes at different chromosomal loci). Also called HLOD score.
heterozygous genotype
(HEH-teh-roh-ZY-gus JEE-noh-tipe)
Occurs when the two alleles at a particular gene locus are different. A heterozygous genotype may include one normal allele and one mutation, or two different mutations. The latter is called a compound heterozygote.
HLOD 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. An HLOD score is calculated in the presence of locus heterogeneity (when the same phenotype can be caused by mutations in genes at different chromosomal loci). Also called heterogeneity logarithm of the odds score.
homozygous genotype
(HOH-moh-ZY-gus JEE-noh-tipe)
Occurs when both alleles at a particular gene locus are the same. A person may be homozygous for the normal allele or for a mutation.