Prior to cell division, a cell duplicates its DNA through DNA replication. To enable the replication machinery to access the template strands, the double-stranded DNA molecule must be unwound and separated. This function is performed by the enzyme helicase.
Helicase attaches to the DNA at the replication fork. It then disrupts the hydrogen bonds between complementary base pairs, thereby unwinding the double helix and separating the two strands into single strands. These single strands subsequently act as templates for the synthesis of new DNA strands.
The other enzymes involved in DNA replication have distinct functions:
- DNA polymerase: Creates new DNA strands by incorporating nucleotides that are complementary to the template strand.
- Ligase: Connects Okazaki fragments on the lagging strand through the formation of phosphodiester bonds.
- Primase: Produces short RNA primers, which serve as initiation sites for DNA polymerase to commence synthesis.
Consequently, helicase is the enzyme responsible for unwinding the double helix and separating the DNA strands.