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Difference between DNA polymerase 1 and 3

DNA polymerase 1 vs 3

DNA polymerases are specially designed enzymes which help in formation of DNA molecules by assembling tiny building blocks of DNA called as nucleotides. DNA polymerase helps in splitting of the DNA molecule into two identical DNAs. This process of DNA splitting is called as DNA replication. DNA polymerase act as a catalyst in DNA replication and hence is very essential. DNA polymerase helps in reading the already existing DNA strands to create two new strands that match the original existing DNA. In this way, the genetic information is forwarded into the daughter cells and transmitted from one generation to another.

Difference in Structure

There are many varieties of DNA polymerases based on the different functions they have to perform. DNA polymerase 1 is essential for DNA replication and it is also called as Pol 1. It was discovered by Arthur Kornberg. DNA polymerase 3 is essential for pro-karyotic DNA replication and was discovered by Thomas Kornberg and Malcolm Gefter. DNA polymerase 3 is also called as holoenzyme and it is the most essential component of replisome.

Difference in function

DNA polymerase 1 functions helps in DNA replication. It is used for molecular biology research. During the process of replication, an RNA primer is filled in the lagging strand of the DNA. DNA polymerase 1 removes the RNA primer and fills in the nucleotides which are necessary for the formation of the DNA in the direction- 5’ to 3’. It also helps in proof reading to see if there is any mistake done while replication and while matching base pairs. The fact that must be remembered is that this DNA polymerase 1 only adds the nucleotides but does not join them. DNA joining is done by another enzyme called as ligase which forms continuous strands of DNA. The main function of DNA polymerase 1 is DNA labeling by nick translation and second strand synthesis of cDNA. DNA polymerase 1 also catalyzes 5’ to 3’ synthesis of DNA. DNA polymerase 1 reads the shape and polarity of the incoming dNTP. DNA polymerase 1 has 3 activities like polymerase, 3’ to 5’ exonuclease and 5’ to 3’ exonuclease. DNA polymerase 1 is a template dependent DNA polymerase.

The Pol 3 catalytic centre has tightly bound subunits called alpha, epsilon and theta. The alpha subunit is responsible for the DNA polymerase activity, the epsilon subunit has proof reading exonuclease activity and the theta subunit is the smallest of all and helps in enhancing the proof reading properties of epsilon. A Replisome is located at the replication fork. DNA polymerase 3 is a component of the replisome and hence helps in replication.


DNA polymerase 3 is essential for the replication of the leading and the lagging strands whereas DNA polymerase 1 is essential for removing of the RNA primers from the fragments and replacing it with the required nucleotides. These enzymes cannot replace each other as both have different functions to be performed. DNA polymerases help in transferring the genetic information and the traits from one generation to another through the process of DNA replication.

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