introduction of rna virus evolution

lots of viruses, in particular rna viruses, have high mutation rates and relatively short generation times. particle stability during infection in nature or in laboratory triggers the evolutionary event toward different mechanisms such as genome segmentation, point mutation and  recombination. the frequency of mutant genomes increase and modify  the previous distribution, which, consequently, lead to emergence of a new infectious particle. mutation and selection are the most fundamental processes in evolution. high mutation rate of rna viruses has an important role in viral fitness. therefore, it increase our understanding about molecular biology of viral infections and their evolution by selection, mutation could reliably  determine our ability to challenge destructive viruses. this review focuses on existing impressions of genetic organization and mechanisms of rna viruses evolution.