Replikaatiohaarukoiden

Replikaatiohaarukoiden, or replication forks in English, are Y-shaped structures that form during DNA replication. They are the sites where the DNA double helix is unwound and separated into two single strands, which then serve as templates for the synthesis of new complementary strands. This process is fundamental to cell division and the transmission of genetic information.

The formation of a replication fork is initiated by an enzyme called helicase, which breaks the hydrogen bonds holding the two DNA strands together. Single-strand binding proteins then attach to the separated strands to prevent them from re-annealing. DNA polymerase, the enzyme responsible for synthesizing new DNA, can only add nucleotides to an existing strand, so an enzyme called primase synthesizes short RNA primers that provide a starting point for DNA polymerase.

Replication proceeds bidirectionally from origins of replication, meaning that two replication forks move away from each origin in opposite directions. One strand, the leading strand, is synthesized continuously in the 5' to 3' direction, following the movement of the replication fork. The other strand, the lagging strand, is synthesized discontinuously in short fragments called Okazaki fragments, also in the 5' to 3' direction, but in the opposite direction of the fork's movement. These fragments are later joined together by DNA ligase. The coordinated action of all these components at the replication fork ensures the accurate and efficient duplication of the entire genome.