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1. The range of minor alterations present in a genome, such as the number of diverse alleles of a specific gene that are found as a result of small mutations in the DNA of a species.
2. The expression of those diverse genes in living organisms and their impact on health or disease.
genetic variability a range of phenotypes for a particular CHARACTER produced by alternative alleles of one or more genes, the range containing discrete groups (see QUALITATIVE INHERITANCE or a continuous spectrum of types (see POLYGENIC INHERITANCE). Genetic variability arises initially by MUTATION and is maintained by sexual reproduction involving CROSSING OVER in MEIOSIS. Such variation is the raw material for NATURAL SELECTION to act upon, ensuring that the best-adapted variants are most likely to reproduce.