What is the primary role of primase during DNA replication?

Introduction / Context:
DNA polymerases require a free 3'-OH to begin nucleotide addition. Primase solves the initiation problem at both leading and lagging strands.

Given Data / Assumptions:

• Replication fork contains helicase, primase, and DNA polymerases.
• DNA polymerase cannot start de novo; it extends from an existing 3'-OH.

Concept / Approach:
Primase (an RNA polymerase) synthesizes short RNA primers that provide the necessary 3'-OH for DNA polymerase to extend.

Step-by-Step Solution:
1) Primase lays down an RNA primer complementary to template DNA.2) DNA polymerase extends from the primer, copying the template.3) On the lagging strand, primase must act repeatedly to start Okazaki fragments.

Verification / Alternative check:
Biochemical reconstitutions show loss of synthesis initiation when primase is omitted; adding primase restores initiation capability.

Why Other Options Are Wrong:
Removal of primers is done by nucleases and replacement polymerases; helicase unwinds DNA, not primase; proofreading is a function of 3'→5' exonuclease activity in certain DNA polymerases.

Common Pitfalls:
Assuming DNA polymerase can start without a primer or confusing primase with helicase.

Final Answer:
Synthesize a short RNA primer to initiate DNA synthesis