“Might as Well Jump!” Template Switching by Retroviral Reverse Transcriptase, Defective Genome Formation, and Recombination

High evolutionary potential and genetic variation in retroviral populations depend upon the mutation and recombination rates per replication cycle, the replication rate (replication cycles per time), and the selective forces that act on the population. The virally encoded reverse transcriptases lack proofreading capability and are evolutionarily selected for jumping (switching templates) during reverse transcription. One consequence of the template switching nature of reverse transcriptases is a high rate of intramolecular template switching, which leads to defective genome formation; another consequence is intermolecular template switching between two copackaged genomic RNAs, which leads to recombination.