In DNA replication, what is the primary function of RNA primase?

• A. It joins Okazaki fragments on the lagging strand by sealing nicks in the sugar-phosphate backbone.
• B. It unwinds the DNA double helix ahead of the replication fork by breaking hydrogen bonds between base pairs.
• C. It synthesizes short RNA primers that provide a free $3\prime OH$ group for DNA polymerase to begin DNA synthesis.
• D. It proofreads newly synthesized DNA and removes mismatched nucleotides using exonuclease activity.

Answer: (C)

Verified step by step guidance

1. Understand the role of RNA primase in DNA replication: RNA primase is an enzyme that synthesizes a short RNA segment called a primer.
2. Recognize that DNA polymerase, the enzyme responsible for synthesizing new DNA strands, cannot start DNA synthesis on its own; it requires a free 3\' hydroxyl (3\' OH) group to add nucleotides.
3. Identify that RNA primase provides this free 3\' OH group by creating a short RNA primer complementary to the DNA template strand.
4. Note that this RNA primer serves as the starting point for DNA polymerase to begin adding DNA nucleotides and extend the new DNA strand.
5. Distinguish RNA primase's function from other enzymes: it does not join Okazaki fragments, unwind DNA, or proofread DNA; its primary role is to synthesize RNA primers.