“DNA polymerase synthesizes the DNA while RNA polymerase synthesizes the RNA.”
Enzymes are the class of proteins that helps in catalyzing different biological reactions. A polymerase is one of the enzymes that synthesize nucleic acids.
The nucleic acid is present in the nucleus of a cell either DNA or RNA (RNA in case of the only retrovirus) which is our genetic material. The DNA has all the information of an organism which it transfers from one generation to another.
For that by following the central dogma process- a collective process of replication, transcription and translation, DNA forms different proteins.
Through the replication, the DNA becomes doubled, which is transcribed into functional mRNA. The mRNA has all the information to form a specific protein. The mRNA translated into a long chain of amino acids which ultimately form a specific protein.
The polymerases are the hero of the entire central dogma process. Thus we are discussing all this.
Read more on DNA replication: General process of DNA replication.
Either DNA polymerase or RNA polymerase is involved in this, however, both are different and perform a different function.
In the present article, we will discuss some of the important differences between both of our heroes which you will never get on the internet.
So let’s starts the article,
DNA polymerase Vs RNA polymerase:
Obviously, the first difference is the molecules they synthesize.
“The DNA polymerase synthesizes DNA strand while the RNA polymerase synthesizes the RNA strand”
DNA synthesis occurs during replication, thus the DNA polymerase functions during the replication, always.
While the RNA polymerase functions during the process of transcription (RNA synthesis only occurs during transcription).
The DNA is a double-stranded molecule, while the RNA is single-stranded- formed from the DNA during transcription.
Based on that, another difference between both is that the DNA polymerase manufacture double-stranded DNA while the RNA polymerase manufacture a single-stranded RNA.
Because of that, the DNA polymerase always required a short-single-stranded DNA/RNA molecule- called primer for starting the synthesis, which is not required for RNA polymerase.
The DNA polymerase only inserted nucleotides once it finds the free 3’ OH end facilitated by the primer-synthesize by the primase enzyme.
But that is not the case with RNA polymerase, RNA polymerase adds nucleotides directly.
Therefore, the synthesis process governed by the DNA polymerase is not de novo while the RNA polymerase synthesizes RNA by de novo.
The DNA polymerase adds dATP, dGTP, dCTP and dTTP to the growing DNA strand while the RNA polymerase inserts dATP, dGTP, dCTP and dUTP to the growing RNA strand.
(Because instead of thymine, the RNA contains uracil).
Though the function of both polymerases is to synthesize nucleic acid, both are functionally different.
The DNA polymerase has polymerization as well as proofreading activity while the RNA polymerase only has the polymerization activity.
DNA polymerase inserts nucleotides and repairs the mismatched pairing by its proof-reading activity.
In the process of proofreading – also known as exonuclease activity, the DNA polymerase trackback on the growing strand, the exonuclease domain of it removes the mismatch and the polymerization domain inserts new nucleotide in place of it.
On the other side, the RNA polymerase does not have exonuclease activity, thus it can not repair the mismatch. Because of this reason, the error rate of the DNA polymerase is much lower than the RNA polymerase.
The rate of polymerization through the DNA polymerase is approximately 1000 nucleotides per second (prokaryotes) while the rate of RNA polymerase is 40 to 80 nucleotides per second.
We can say that the DNA polymerase is faster, efficient and more accurate while the RNA polymerase is slower, inefficiently and inaccurate.
DNA polymerase has three different subtypes while RNA polymerase has five different subtypes (eukaryotes).
The end process of synthesis is also different in both.
The DNA continues the synthesis of DNA until the end when the strand ends, the polymerization stops. Hence synthesizes entire chromosomal DNA.
But RNA polymerase is different. The polymerization through RNA polymerase is terminated when finds the stop codon or termination codon on the nucleic acid strand.
Both govern the catalytic reaction in different stages of the cell cycle.
The DNA polymerase functions during the S1 phase of a cell cycle while the RNA polymerase functions during the G1 and G2 phase of it.
During the replication, four different single-stranded DNA (two double-stranded DNA) are formed at the end of it
The duplex DNA must unwind continuously for DNA polymerase to work.
The DNA polymerase required another enzyme called helicase unwinding of DNA to facilitate single-stranded template DNA. In addition to this, it also required DNA topoisomerase to release tension from the remaining dsRNA strand.
Contrary to this, the RNA polymerase does not require any unwinding process and so no helicase required in the synthesis process.
However, a holoenzyme is needed for the activation of RNA polymerase.
The summary of the differences between DNA polymerase vs RNA polymerase are shown in the table below,
|Difference||DNA polymerase||RNA polymerase|
|Synthesis||Manufacture DNA||Manufacture RNA|
|Activity||Polymerization as well as proof-reading||Only polymerization|
|Process||Involved in replication||Involved in transcription|
|Nucleotides||A, T, G and C||A, U, G and C|
|Cell division||During S1 phase||During G1 and G2 phase|
|Additional enzyme||Helicase and topoisomerase||Holoenzyme|
|Error rate||Very low (due to proof-reading activity)||Very high|
|Speed of polymerization||High||Low|
|Process||Not de novo||De novo|
DNA polymerase in a nutshell:
DNA polymerase is an enzyme that synthesizes DNA in all living organisms and is thus present in almost all organisms on earth. It helps in replication to copy DNA using the single-stranded primer- either DNA or RNA.
The DNA polymerase can not replicate DNA de novo, it required a free 3’ OH group to do so which is provided by the primer.
It has polymerization, as well as exonuclease, domain and because of that, it has the power to repair the mismatches too.
It has 5’ to 3’ polymerization activity and 3’ to 5’ and 5’ to 3’ exonuclease activity.
5 different DNA polymerase in prokaryotes and 4 different polymerase families are present in eukaryotes.
The precision, efficiency and speed of DNA polymerase are much higher with accuracy. With the help of DNA helicase, the DNA polymerase unwinds dsDNA for facilitating replication.
Besides polymerization and exonuclease activity, several other functions of DNA polymerase are
V(D)J segment recombination, gap filling, antigen diversity, maintaining the length of telomere, DNA repair pathway and somatic hypermutation.
If you want to learn more about the different types of DNA polymerase, its function, mechanism of action and other related information, read our article: Multifunctional DNA polymerase.
RNA polymerase in a nutshell:
As like the DNA polymerase, the RNA polymerase is also present in all living organism, however, functions differently.
It synthesizes single-stranded RNA during the transcription process.
It required a holoenzyme to function properly, although does not have a proofreading activity. Hence the error rate of the RNA polymerase is much higher than the DNA polymerase.
The RNA polymerase is slow, inefficient and adds nucleotides 40 to 50 per second. But like DNA polymerase, RNA polymerase is also important for a cell.
If it is not present, how can the mRNA be synthesized? therefore, Give it equal respect as like DNA polymerase. ?
In 1956, the first DNA polymerase was discovered by Arther Kornberg. Both polymerases are important for a cell.
Error in the function of the polymerase (either DNA polymerase or RNA polymerase) results in some abnormalities. These abnormalities may cause some serious genetic problems.
wrong nucleotide addition during replication of transcription results in an abnormal polypeptide chain and results in abnormal or non-function protein.