DNA replication is the fundamental process by which cells duplicate their genetic material before division. This semi-conservative process ensures that each new DNA molecule contains one original template strand and one newly synthesized strand, maintaining genetic fidelity across generations.
DNA replication begins at specific sites called origins of replication. The helicase enzyme unwinds the double helix by breaking hydrogen bonds between base pairs, creating a Y-shaped structure called the replication fork. Single-strand binding proteins, or SSBPs, immediately bind to the separated strands to prevent them from re-annealing and protect them from degradation.
Before DNA synthesis can begin, primase synthesizes short RNA primers on both template strands. These primers provide the essential 3'-OH group that DNA polymerase requires to start adding nucleotides. On the leading strand, synthesis is continuous toward the replication fork. On the lagging strand, synthesis is discontinuous, creating short segments called Okazaki fragments, each requiring its own primer.