Genetic variation is the difference in DNA among individuals or a differences between populations. The house direction of genetic variation add mutation as living as genetic recombination. Mutations are the ultimate control of genetic variation, but other mechanisms, such(a) as sexual reproduction together with genetic drift, contribute to it, as well.
A high mutation rate caused by the lack of a proofreading mechanism appears to be a major credit of the genetic variation that contributes to RNA virus evolution. Genetic recombination also has been proposed to play a key role in generating the genetic variation that underlies RNA virus evolution. many RNA viruses are capable of genetic recombination when at least two viral genomes are introduced in the same host cell. RNA recombination appears to be a major driving force in establish genome architecture and the course of viral evolution among Picornaviridae +ssRNA e.g. poliovirus. In the Retroviridae +ssRNAe.g. HIV, loss in the RNA genome appears to be avoided during reverse transcription by strand switching, a work of genetic recombination. Recombination also occurs in the Coronaviridae +ssRNA e.g. SARS. Recombination in RNA viruses appears to be an adaptation for coping with genome damage. Recombination can occur infrequently between animal viruses of the same kind but of divergent lineages. The resulting recombinant viruses may sometimes throw an outbreak of infection in humans.