second, the dynamic choice model, suggests that reverse transcriptase changes templates when the RNAse function and the polymerase function are not in sync rate-wise, implying that recombination occurs at random and is not in response to genomic damage. A study by Rawson et al. supported both models of recombination. From 5 to 14 recombination events per genome occur at each replication cycle. Template switching (recombination) appears to be necessary for maintaining genome integrity and as a repair mechanism for salvaging damaged genomes. Applications Antiviral drugs As HIV uses reverse transcriptase to copy its genetic material and generate new viruses (part of a retrovirus proliferation circle), specific drugs have been designed to disrupt the process and thereby suppress its growth. Collectively, these drugs are known as reverse-transcriptase inhibitors and include the nucleoside and nucleotide analogues zidovudine (trade name Retrovir), lamivudine (Epivir) and tenofovir (Viread), as well as non-nucleoside inhibitors, such as nevirapine (Viramune). Molecular biology Reverse transcriptase is commonly used in research to apply the polymerase chain reaction technique to RNA in a technique called reverse transcription polymerase chain reaction (RT-PCR). The classical PCR technique can be applied only to DNA strands, but, with the help of reverse transcriptase, RNA can be transcribed into DNA, thus making PCR analysis of RNA molecules possible. Reverse transcriptase is used also to create cDNA libraries from mRNA. The commercial availability of reverse transcriptase greatly improved knowledge in the area of molecular biology, as, along with other enzymes, it allowed scientists to clone, sequence, and characterise RNA. See also cDNA library DNA polymerase msDNA Reverse transcribing virus RNA polymerase Telomerase Retrotransposon marker References External links animation of reverse transcriptase action and three reverse transcriptase inhibitors Molecule of the month (September 2002) at the RCSB PDB HIV Replication 3D Medical Animation. (Nov 2008). Video by Boehringer Ingelheim. TWiV 904: 50 years of reverse transcriptase Vincent Racaniello travels to Cold Spring Harbor Laboratory to speak with David Baltimore, John Coffin (scientist), and Harold Varmus about the discovery in 1970 of retroviral reverse transcriptase and its impact on life sciences research. Genetics EC 2.7.7 Molecular biology Viral enzymes Telomeres 1970 in biology RNA reverse-transcribing viruses