Picture from: http://www.web-books.com/MoBio/Free/Ch4J1.htm
The central dogma of biology commonly seen is thus:
- DNA --> RNA --> Protein
However, this not entirely accurate as there are other pathways as well. Reverse transcription is the process of forming a DNA product from an RNA template.
Discovery[]
Reverse transcriptase (als known as RNA dependent DNA polymerase) was discovered by Howard Temin and David Baltimore. Their work later gained them the Nobel Prize for Physiology and Medicine in 1975.
In 1961, Temin was studying RNA viruses. The instability of an RNA genome led him to believe that the RNA was converted into DNA. Baltimore seperately was also working with viruses. Both scientists independently performed the same set of experiments.
The experiments began with a pure culture of virus that was disrupted using detergent. Next, radiolabeled deoxythymidine triphosphate (dTTP) was added to the mix. The men then observed that the dTTP was incorporated into the DNA. When radiolabled ribonucleotide triphosphate (rNTP) was added, no RNA synthesis was observed. To confirm that the product truely was DNA, RNase and DNase were added. The product was only affected by DNase.
Information obtained from: http://basic.shsmu.edu.cn/jpkc/cellbiota/resource/exper/19.pdf
How it Works[]
Reverse transcriptase transcribes a single stranded RNA template into single stranded DNA.
- A tRNA is used as a primer by annealing is 3' end of an unwound section to the primer binding site on the RNA
- A DNA sequence complementary to the RNA's U5 and R sequences is extended from the tRNA
- RNase H degrades the U5 and R sequences
- The DNA/tRNA unit "jumps" to the remaining R sequence of the RNA (at the 3' end)
- The RNA genomic material is transcribed and the DNA extends
- The majority of the RNA is degraded by RNase H
- A second DNA strand extends from the 3' end of the remaining RNA
- The tRNA and remaining RNA are degraded by RNase H
- The second DNA strand "jumps" and its PBS hybridizes with the first DNA strand's PBS
- Both DNA strands extend
Information paraphrased from: http://www.web-books.com/MoBio/Free/Ch4J1.htm