| Enzyme |
Function |
| DNA Helicase |
These proteins bind to the double stranded DNA helix and initiate the separation of the two strands by breaking the hydrogen bonds. |
| DNA single-stranded binding proteins (SSBs) |
These proteins bind to the DNA strands and keep them separated by blocking the formation of new hydrogen bonds. |
| DNA Gyrase |
This enzyme relieves the tension produced from the unwinding of DNA by the DNA Helicase at the beginning of the replication.
*A bacterial enzyme. |
| DNA Polymerase I |
This enzyme is primarily used for removing RNA primers from the lagging strand and filling in the necessary nucleotides of the Okazaki fragments in 5'-3' direction, while also proofreading for mistakes. |
| DNA Polymerase III |
This enzyme has a number of different functions:
The polymerase "reads" a DNA strand as a template and uses it to synthesize a new strand. It can build complementary bases only in the direction of 5’ to 3’ which results in synthesis of the new strand in a 5'-3'. |
| Primase |
The Primase enzyme synthesizes a short RNA segment on the DNA strand. Although it function is very simple, the Primase is has a key role in DNA replication because DNA polymerases cannot initiate the synthesis of a DNA strand without an initial RNA primer. |
| DNA ligase |
The function of this enzyme to join any not bonded DNA fragments by forming phosphodiester bonds between 3' hydroxyl group of one nucleotide with the 5' phosphate group of another. |
| Exonuclease |
This enzyme can be DNA Polymerase I or III. It repairs wrong nucleotides at the end of each DNA strand, by adding the correct nucleotides to the complementary strand. It ensures the quality of newly formed DNA strands. |
