What are the key enzymes involved in DNA replication?

The key enzymes involved in DNA replication are DNA polymerase, DNA helicase, DNA ligase, and primase.

DNA replication is a complex process that involves several enzymes, each playing a crucial role. The first enzyme involved is DNA helicase, which unwinds the double helix structure of the DNA molecule, separating the two strands and creating a 'replication fork'. This unwinding exposes the bases on each strand, allowing them to be read and copied.

Next, the enzyme primase synthesises a short RNA primer on each template strand. These primers serve as starting points for the next enzyme, DNA polymerase. DNA polymerase is responsible for adding new nucleotides to the growing DNA strand, following the base pairing rules of adenine (A) with thymine (T), and cytosine (C) with guanine (G). However, DNA polymerase can only add nucleotides in one direction, from 5' to 3'. This means that one strand, known as the leading strand, is synthesised continuously, while the other strand, known as the lagging strand, is synthesised in fragments called Okazaki fragments.

Finally, the enzyme DNA ligase comes into play. DNA ligase seals the gaps between the Okazaki fragments on the lagging strand, creating a continuous DNA molecule. It also replaces the RNA primers with DNA.

In addition to these main enzymes, there are several others that play supporting roles in DNA replication. For example, topoisomerases relieve the tension in the DNA molecule that is created by the unwinding action of helicase. Single-strand binding proteins bind to the separated DNA strands to prevent them from re-forming the double helix before replication is complete.

In summary, DNA replication is a highly coordinated process that involves a team of enzymes working together. Each enzyme has a specific role, and the process would not be possible without their combined actions.