How is DNA replicated in cells?

DNA replication is the process by which a cell copies its DNA before cell division, ensuring that each daughter cell receives an identical set of genetic information. This process is semi-conservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.

Replication begins at specific sites called origins of replication. The enzyme helicase unwinds the double helix by breaking hydrogen bonds between base pairs, forming a replication fork. Single-strand binding proteins stabilize the separated strands.

The enzyme DNA polymerase synthesizes new DNA strands by adding nucleotides complementary to the template strand in the 5' to 3' direction. One strand, called the leading strand, is synthesized continuously, while the lagging strand is synthesized discontinuously in short fragments known as Okazaki fragments.

These fragments are later joined together by the enzyme DNA ligase. Another enzyme, primase, synthesizes RNA primers that provide a starting point for DNA polymerase.

Proofreading mechanisms ensure high accuracy during replication by correcting errors as they occur.

Overall, DNA replication is a precise and regulated process that maintains genetic continuity across cell generations.