DNAreplikointiin

DNAreplikointiin is the biological process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. This process is essential for cell division, growth, and repair. In eukaryotes, DNA replication occurs during the S phase of the cell cycle.

The process begins with the unwinding of the DNA double helix by an enzyme called helicase. This creates a replication fork, where each strand of DNA serves as a template for the synthesis of a new complementary strand. An enzyme called primase synthesizes short RNA primers, which are necessary to initiate DNA synthesis.

DNA polymerase then adds nucleotides to the 3' end of the primer, extending the new DNA strand. Because DNA polymerase can only add nucleotides in the 5' to 3' direction, one strand, the leading strand, is synthesized continuously. The other strand, the lagging strand, is synthesized discontinuously in short fragments called Okazaki fragments. These fragments are later joined together by another DNA polymerase and DNA ligase.

DNA replication is a highly accurate process, but errors can occur. Mismatch repair mechanisms are in place to correct these errors, ensuring the fidelity of DNA replication. The result of DNA replication is two identical DNA molecules, each consisting of one original strand and one newly synthesized strand. This semi-conservative nature of replication is crucial for maintaining genetic information across cell generations.