Canadian Medical Guide > Biological Sciences > Genetic Phenomena > Variation (Genetics) Terms and Definitions

Variation (Genetics)

Medical Definition:	The phenotypic and genotypic differences among individuals in a population.
Previously Indexed:	Genetics (1966-1967),Genetics, Population (1966-1967)

Variation (Genetics) Categories.

	Genetic Heterogeneity - The presence of apparently similar characters for which the genetic evidence indicates that different genes or different genetic mechanisms are involved in different pedigrees. In clinical settings genetic heterogeneity refers to the presence of a variety of genetic defects which cause the same disease, often due to mutations at different loci on the same gene, a finding common to many human diseases including ALZHEIMER DISEASE; CYSTIC FIBROSIS; LIPOPROTEIN LIPASE DEFICIENCY, FAMILIAL; and POLYCYSTIC KIDNEY DISEASES. (Rieger, et al., Glossary of Genetics: Classical and Molecular, 5th ed; Segen, Dictionary of Modern Medicine, 1992)
	Mutation - Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.
	Polymorphism (Genetics) - The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequence visible at a chromosomal level.

Variation (Genetics) Medical Definitions and Terms

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