DNA replication is a process whereby a single DNA molecule produces two identical copies. Each side of the DNA’s double-helix structure extends in the opposite direction, allowing it to split down the middle. Once split, each side serves as a template for a new strand. In the case of prokaryotic cells, the process occurs in the cytoplasm, whereas in eukaryotic cells, the replication occurs in the nucleus.
The process of DNA replication follows three steps: initiation, elongation and termination. The initiator proteins start the replication process at specific points in the DNA, which are commonly referred to as origins. After the origin is determined, the initiator proteins recruit other proteins to form a protein complex that is responsible for the splitting of the DNA strands.
During the elongation step, an enzyme called DNA polymerase adds nucleotides to the right end of the sequence of the newly formed strand. The template strand determines which DNA nucleotide is added at specific positions along the chain. RNA polymerase initiates the synthesis of the new strands by creating an RNA polynucleotide strand that is complementary to the template created by the DNA polymerase.
The termination step takes place when the DNA replication fork, a structure featuring two prongs of single DNA strands, either stops or is blocked. This step is the result of the interaction between a termination site sequence within the DNA and a protein that binds to the sequence to end the DNA replication process.