DNA duplicates itself with complete fidelity for passing on genetic information to the next generation of cells. Replication may be defined as a mechanism for transmission of genetic information generation after generation.
Replication occurs through the following steps:
1. Unwinding of DNA double helix
The two strands of the replicating DNA molecule separate by the action of the enzyme Helicase. Topoisomerase enzyme keeps it open. The opened part is the replication fork.
2. Synthesis of the primer
Primer is a short RNA molecule of about 5 to 10 bases. It is formed in the presence of the enzyme primase. The primer provides a 3’-OH group for attachment of the new DNA strand.
3. Synthesis of new DNA strand
The opened strands of DNA form the template. New strands complementary to template get synthesized. At the replication fork, a new DNA strand begins to synthesize, attaching itself to the primer, in the presence of the enzyme DNA polymerase.
It begins synthesis from its 5’ end and a DNA strand complementary to one of the unwound parental DNA strand gets synthesized. The new strand of DNA continues to be synthesized uninterrupted and is termed as the leading strand.