replikointivaiheita

Replikointivaiheita refers to the stages of DNA replication. This fundamental biological process ensures that a cell's genetic material is accurately copied before cell division. DNA replication can be broadly divided into three main phases: initiation, elongation, and termination.

Initiation is the starting point where the DNA double helix unwinds. Specific proteins, known as helicases, break the hydrogen bonds holding the base pairs together, creating replication forks. These forks are Y-shaped structures where the actual copying of DNA occurs. Primase then synthesizes short RNA primers, which are necessary to start the DNA synthesis process.

Elongation is the phase where new DNA strands are synthesized. DNA polymerase enzymes, the workhorses of replication, add complementary nucleotides to the template strands. Because DNA polymerase can only add nucleotides in one direction (5' to 3'), one new strand, the leading strand, is synthesized continuously. The other strand, the lagging strand, is synthesized discontinuously in short fragments called Okazaki fragments, which are later joined together by DNA ligase.

Termination occurs when the replication process is completed. In circular bacterial chromosomes, replication forks meet at a specific termination site. In linear eukaryotic chromosomes, replication continues until the ends of the chromosomes, called telomeres, are reached. Enzymes then clean up any remaining RNA primers and seal any gaps in the DNA backbone, resulting in two complete DNA molecules.