Which enzyme is crucial for initiating DNA replication?

Primase is essential for initiating DNA replication because it synthesizes short RNA primers that provide a starting point for DNA polymerases to begin replication. During the replication process, DNA polymerases cannot initiate the synthesis of a new DNA strand on their own; they require an existing strand of nucleic acid to add nucleotides. Primase synthesizes these RNA primers complementary to the DNA template, which allows DNA polymerases to then extend the new DNA strands by adding nucleotides to the RNA primers.

In DNA replication, various enzymes play specific roles, but the role of primase is particularly critical for creating the primers needed for the entire process to start. Without primase, there would be no short RNA segments available for DNA polymerases to attach to, effectively halting the replication process at the very start. This role distinguishes primase from other enzymes involved in DNA replication.