Replisointi

Replisointi, also known as DNA replication, is the biological process of producing two identical replicas of DNA from one original DNA molecule. This process is crucial for cell division, as each new cell must contain a complete set of the organism's genetic material. Replisointi is a semi-conservative process, meaning that each new DNA molecule consists of one original strand and one newly synthesized strand.

The process begins with the unwinding of the DNA double helix by an enzyme called helicase. This creates a replication fork, where the two strands of DNA separate. Each separated strand then serves as a template for the synthesis of a new complementary strand. The enzyme DNA polymerase is responsible for adding new nucleotides to the growing strand, following the base-pairing rules (adenine with thymine, and guanine with cytosine). Because DNA polymerase can only add nucleotides in one direction (5' to 3'), one of the new strands, called the leading strand, is synthesized continuously. The other strand, the lagging strand, is synthesized in short fragments called Okazaki fragments, which are later joined together by another enzyme called DNA ligase.

Replisointi is a highly accurate process, with proofreading mechanisms in place to correct errors. However, occasional mutations can still occur, which can have various consequences for the organism. The precise control of replisointi is essential for maintaining genetic stability and preventing diseases like cancer.