Genetic variability?

Genetic variability describes genetic diversity. Typically, there isn't just one single expression of a gene; Rather, there are multiple variants, called alleles. For example, there's an allele for black fur and an allele for red fur, and so on. Such different gene variants arise through mutation and, over time, accumulate in the gene pool—the totality of all alleles in a population—provided they aren't detrimental to survival. The more different alleles there are in the gene pool, the greater the population's genetic variability.