Free online lectures on Biochemical Genetics by Biochemistry Club
- DNA serves as a template for replication by DNA polymerase and for the RNA synthesis during transcription, catalyzed by
DNA-dependent RNA polymerases (transfer of information from DNA to RNA).
- Reverse transcription process occurs when DNA is synthesized on an RNA template.
- It is catalyzed by a RNA-dependent DNA polymerase, Reverse transcriptase found in retroviruses causing tumors & other diseases (e.g., Rous sarcoma, AIDS).
- When a retrovirus infects a cell, it forces the cell to synthesize DNA that reproduces the genetic information of the viral RNA.
- The virus has a Reverse transcriptase which catalyzes the incorporation of deoxynucleotides in the 5′→3′ direction to assemble a DNA strand complementary to the RNA strand of the intruder.
- The ribonuclease activity of the same enzyme promotes the hydrolysis of the original RNA template strand & releases the newly formed DNA strand.
- This serves as a template to build another chain of complementary DNA & to obtain a double helix with the genetic information of the viral RNA.
- This double helix, called Proviral DNA, has sequences at both ends called, long terminal repeats containing signals for integration into the host cell DNA, and subsequent transcription of RNA identical to that of the virus.
- Azidothymidine (AZT) – antiviral, used in the treatment of AIDS, inhibits the reverse transcriptase.
- Initially, it was thought that reverse transcription was exclusive to the retrovirus.
- The process also occurs in bacteria and eukaryotic cells.
- Example is Telomerase, which has reverse transcriptase activity.
COMPLETE LESSONS ON GENETICS ARE AVAILABLE IN BIOCHEMISTRY II. CLICK BIOCHEMISTRY II AND THEN GENETICS AND THEN CLICK THE CURRICULUM TAB.