What is the purpose of primase in DNA replication?

Primase plays a critical role in DNA replication by synthesizing short RNA primers that serve as starting points for DNA synthesis. During replication, DNA polymerases are responsible for adding nucleotides to a growing strand; however, they can only add nucleotides to an existing strand. This is where primase comes in: it synthesizes these RNA primers complementary to the template strand.

The RNA primer provides the necessary 3' hydroxyl group that allows DNA polymerase to begin adding DNA nucleotides. Without the action of primase, DNA polymerases would be unable to initiate DNA synthesis, which is essential for both the leading and lagging strands during replication.

This function underscores the importance of primase in ensuring that replication can efficiently proceed, facilitating the accurate duplication of the entire DNA molecule.