Wednesday, 30 December 2020

DNA Polymerase vs RNA Polymerase

* DNA polymerase

• DNA polymerase is an enzyme that synthesizes the double-stranded DNA molecule.

• Molecular weight of DNA polymerase is 400 k Dalton.

• DNA polymerase's mechanism is during DNA replication where by it synthesizes new DNA strands

• DNA polymerase contains 10 subunits.

• The DNA polymerase  replication mechanism is initiated by a short DNA/RNA primer

• DNA polymerase inserts nucleotide bases after finding the free 3' OH group end by the assistance of the primer-synthesizer, primase enzyme

• DNA polymerase adds deoxy Nucleotide triphosphate (dNTP) molecules like dATP(Adenine), dGTP(Guanine), dCTP(Cytosine) and dTTP(Thiamine) to the growing new DNA strand

• DNA polymerase has polymerization and exonuclease proofreading activity
- Polymerization from 5' to 3'
- Proofreading from 5' to 3' as  
   well as 3' to 5'

• The rate of polymerization by DNA polymerase is about 1000 nucleotide bases per second in prokaryotes

• DNA polymerase enzyme is  efficient, and more accurate considering its proofreading activity.

DNA polymerase has three different subtypes in prokaryotes: Type I, II, and III. and five different subtypes in eukaryotes: α, β, γ, δ, ε.

• The DNA synthesis continues until the end when the strand ends, that is when polymerization stops, thus the entire chromosomal DNA is synthesized.

DNA vs RNA : Comparison and Differences

* RNA polymerase

• RNA polymerase is an enzyme that synthesises a single-stranded RNA molecule

• Molecular weight of RNA polymerase is 500 k Dalton.

• RNA polymerase functions during transcription, which is the synthesis of RNA

• RNA polymerase contains 6 subunits.

• RNA polymerase does not need a primer to initiate transcription

• RNA polymerase adds nucleotides directly. It inserts Nitrogenous bases like Adenine, Guanine, Cytosine and Uracil to the growing RNA strand.

• RNA polymerase only has a polymerization activity.
- Polymerization from 5' to 3'

• The rate of RNA polymerase for adding nucleotide bases is 40 to 80 nucleotide base per second.

• RNA polymerase is, inefficient, and inaccurate many times.

• RNA polymerase has five different subtypes in eukaryotes which are Type I, II, III, IV and V

• The polymerization is terminated when RNA polymerase finds the stop codon or termination codon(UAA, UGA and UAG) on the DNA strand.


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