Final answer:
DNA polymerase acts on both the leading and lagging strands at the replication fork, synthesizing DNA continuously on the leading strand and in Okazaki fragments on the lagging strand, while also performing a proofreading function to maintain genetic accuracy.
Step-by-step explanation:
During normal DNA replication at a replication fork, the enzyme DNA polymerase acts on both the leading and lagging strands. On the leading strand, DNA polymerase synthesizes a new strand of DNA continuously by adding nucleotides in a 5' to 3' direction, complementing the parental 3' to 5' strand. However, due to the anti-parallel nature of the two strands in a DNA molecule, the lagging strand, which complements the 5' to 3' parental strand, is synthesized in short fragments known as Okazaki fragments, also in a 5' to 3' direction.
A helicase enzyme unwinds the DNA double helix, forming the replication fork. Primase sets down RNA primers, which then allow DNA polymerase to synthesize these fragments on the lagging strand. DNA polymerase III is the main enzyme that extends both the leading strand and the Okazaki fragments on the lagging strand. Afterwards, DNA polymerase I replaces RNA primers with DNA nucleotides. Finally, DNA ligase seals the gaps between the Okazaki fragments, forming a continuous strand.
It is essential to note that DNA polymerase also has a proofreading function, which helps correct errors by removing incorrectly matched bases. As such, DNA replication ensures accuracy and fidelity in the transmission of genetic information from one generation to the next.