Genetic variation is important to evolution because it helps to maintain the health of a population by constituting alleles that may be useful in overcoming stresses such as diseases and pests. Without genetic variation, some of the fundamental mechanisms of evolutionary changes would not operate.
Genetic variation cushions the population against change, offering organisms the flexibility to adapt. A population that has a higher variation of alleles has better chances of evolving to adapt to a changing environment. Such organisms are more likely to survive extreme conditions such as drought and disease epidemics.
Genetic variation encompasses the diversity in gene frequencies and refers to the differences between individuals or populations. During inheritance, nucleotides are sometimes reshuffled and recombined, resulting in new recombinations that are different from the parents. Every individual organism is a unique mixture of alleles from its parents.
The primary source of genetic variation is mutation, which refers to changes in the DNA. Mutation refers to a permanent change in the chemical structure of a gene. A single mutation may have far-reaching effects. However, evolutionary changes are often as a result of an aggregation of several mutations. Genetic variation may also be caused by gene flow, which refers to any movement of genes across a population. Sex may also be a source of genetic variation because it introduces new gene combinations into a population.