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Glossary of common termss  p  r  i  n  g    2  0  0  5  

Allele One of several forms of the same gene. Alleles differ in their DNA sequence.
Epistasis Non-additive interactions of genes at different loci.
Gene Functional unit of heredity.
Gene Pool All of the genes contained in a population.
Genotype The genetic or hereditary information borne by an individual, as distinct from an individual's visible features (phenotype).
Heritability The proportation of phenotypic variation in a trait that results from genetic variation.

More formally: h2 = Vg / Vp, where
h2 = heritability,
Vg = phenotypic variance due to genes, and
Vp = total phenotypic variance.

Heterozygous Having, at a particular locus, two different alleles of one gene.
Locus Site on a chromosome occupied by a particular gene.
Mutation A spontaneous change in a genotype.
Overall Heterozygosity The proportion of loci in an individual's genotype which are heterozygous (usually designated as "Ho".
Polymorphism Presence in a population of two or more genotypes for a given trait.
Population A group of organisms of the same species, occupying a particular geographic area and sharing a common gene pool.
Phenotype The visible features of an organism, as contrasted with its genotype.
Phenotype All morphological, physiological, behavioral, biochemical, and other characteristics of an organism which develop through the interaction of genes and the environment (an alternative definition).
Pleiotropy Where a single gene (locus) has phenotypic effects on more than one trait.
Polygenic Inheritance Where two or more genes (loci) interact to affect a phenotypic trait. These interactions can be additive or epistatic.