Editing Complementary DNA (section)

==Viruses and retrotransposons==
Some viruses also use cDNA to turn their viral RNA into mRNA (viral RNA → cDNA → mRNA). The mRNA is used to make viral proteins to take over the host cell.

An example of this first step from viral RNA to cDNA can be seen in the HIV cycle of infection. Here, the host cell membrane becomes attached to the virus' lipid envelope which allows the viral capsid with two copies of viral genome RNA to enter the host. The cDNA copy is then made through reverse transcription of the viral RNA, a process facilitated by the chaperone CypA and a viral capsid associated reverse transcriptase.<ref>{{Cite journal |last=Altfeld |first=Marcus |last2=Gale |first2=Michael Jr. |date=1 June 2015 |title=Innate immunity against HIV-1 infection |journal=Nature Immunology |language=en |volume=16 |issue=6 |pages=554–562 |doi=10.1038/ni.3157 |issn=1529-2908 |pmid=25988887 |s2cid=1577651 |doi-access=free}}</ref>

cDNA is also generated by [[retrotransposon]]s in eukaryotic genomes. Retrotransposons are mobile genetic elements that move themselves within, and sometimes between, genomes via RNA intermediates. This mechanism is shared with viruses with the exclusion of the generation of infectious particles.<ref>{{Cite journal |last=Havecker |first=Ericka R. |last2=Gao |first2=Xiang |last3=Voytas |first3=Daniel F. |date=2004-05-18 |title=The diversity of LTR retrotransposons |journal=Genome Biology |volume=5 |issue=6 |pages=225 |doi=10.1186/gb-2004-5-6-225 |issn=1474-760X |pmc=463057 |pmid=15186483 |doi-access=free}}</ref><ref>{{Cite journal |last=Cordaux |first=Richard |last2=Batzer |first2=Mark A. |date=October 2009 |title=The impact of retrotransposons on human genome evolution |journal=Nature Reviews Genetics |language=en |volume=10 |issue=10 |pages=691–703 |doi=10.1038/nrg2640 |issn=1471-0064 |pmc=2884099 |pmid=19763152}}</ref>