DNAsüntezi

DNAsüntezi, also known as DNA replication, is the biological process by which a double-stranded DNA molecule is duplicated into two identical DNA molecules. This process is fundamental to cell division and heredity, ensuring that genetic information is accurately passed from one generation of cells to the next. DNAsüntezi occurs during the S phase of the cell cycle, before mitosis or meiosis.

The process begins with the unwinding of the DNA double helix by an enzyme called helicase, which breaks the hydrogen bonds between complementary base pairs. This creates a replication fork. Each separated strand then serves as a template for the synthesis of a new complementary strand. DNA polymerase is the primary enzyme responsible for adding new nucleotides to the growing DNA chain, following the base-pairing rules (adenine with thymine, and guanine with cytosine).

Because DNA strands are antiparallel, DNA polymerase can only synthesize new DNA in the 5' to 3' direction. This leads to different synthesis patterns on the two template strands. On one strand, known as the leading strand, synthesis is continuous. On the other strand, the lagging strand, synthesis occurs discontinuously in short fragments called Okazaki fragments, which are later joined together by another enzyme, DNA ligase.

The accuracy of DNAsüntezi is remarkably high, with DNA polymerase possessing proofreading capabilities to correct errors. However, occasional errors can still occur, leading to mutations. The completion of DNAsüntezi results in two identical DNA molecules, each consisting of one original and one newly synthesized strand, a characteristic known as semi-conservative replication.