Reverse Transcriptase
Reverse transcriptase (RT) is an RNA-dependent DNA polymerase enzyme that synthesises a complementary DNA (cDNA) strand using an RNA template, a process called reverse transcription that is the reverse of the normal transcription step in the central dogma. It was discovered independently by Howard Temin and David Baltimore in 1970, a finding that won them the Nobel Prize in Physiology or Medicine in 1975 and fundamentally altered the understanding of genetic information flow. Reverse transcriptase is encoded by retroviruses (including HIV) and retrotransposons, and is an essential biotechnology tool used to create cDNA libraries for cloning, gene expression analysis, and RT-PCR diagnostics.
Key Properties of Reverse Transcriptase
| Property | Detail | Significance |
|---|---|---|
| Template | Single-stranded RNA | Uses mRNA or viral genomic RNA |
| Product | Complementary DNA (cDNA) | Lacks introns, stable in bacteria |
| Additional activity | RNase H activity | Degrades RNA strand of RNA:DNA hybrid |
| Error rate | ~1 error per 2,000–10,000 nt | Higher than DNA pol; drives viral evolution |
| Inhibitors (HIV therapy) | NRTIs, NNRTIs | Key targets for antiretroviral drugs |
| Biotechnology use | RT-PCR, cDNA library construction | Foundational molecular biology tool |
Interactive Tools
Khan Academy — Retroviruses and HIV
Explanation of how retroviruses use reverse transcriptase
Open ToolNCBI Bookshelf — Reverse Transcription
Detailed chapter on retroviral reverse transcription from Molecular Biology of the Cell
Open ToolBrilliant.org — Molecular Biology
Interactive course covering enzyme mechanisms and gene expression exceptions
Open Tool
Wikimedia Commons, CC BY-SA
Related Terms
Central Dogma of Biology
The Central Dogma of Molecular Biology, formulated by Francis Crick in 1958, describes the general flow of genetic information within a biological system: DNA is transcribed into RNA, and RNA is translated into protein. Crick's original statement also specified that information transfer from protein back to nucleic acid does not normally occur, establishing a directional framework for gene expression. The discovery of reverse transcriptase in retroviruses revealed that RNA can also be reverse-transcribed into DNA, representing a known exception to the standard flow while still consistent with Crick's framework.
Gene Cloning
Gene cloning is the process of making multiple identical copies of a specific gene or DNA fragment by inserting it into a vector (such as a plasmid or bacteriophage) and replicating it inside a host organism, typically Escherichia coli. The technique involves cutting both the target DNA and the vector with the same restriction enzyme to generate compatible sticky ends, ligating them with DNA ligase, transforming the recombinant construct into host cells, and selecting colonies that contain the insert. Gene cloning is foundational to modern biotechnology and medicine, enabling the production of recombinant proteins (such as insulin), gene therapy constructs, diagnostic probes, and transgenic organisms.
Restriction Enzyme
A restriction enzyme (restriction endonuclease) is a bacterial enzyme that cuts double-stranded DNA at or near a specific short nucleotide sequence called a recognition site, typically 4–8 base pairs in length. Bacteria produce these enzymes as part of a restriction-modification defence system to degrade foreign viral DNA that lacks the bacterium's own methylation marks. In molecular biology, type II restriction enzymes such as EcoRI and HindIII are indispensable tools for cutting DNA predictably to produce defined fragments with either blunt ends or "sticky" (cohesive) overhangs, enabling gene cloning, restriction mapping, and DNA fingerprinting.
From Latin "reversus" (turned back, past participle of "revertere") + "transcriptase" (the enzyme class for transcription). The name reflects the reversal of the usual DNA→RNA direction. Howard Temin originally called the activity "RNA-dependent DNA polymerase" in his 1970 paper in Nature.