Question

The enzyme responsible for synthesizing RNA primers during DNA replication is -

• A. DNA polymerase
• B. Primase
• C. Topoisomerase
• D. Helicase

Hint:

Remember the key limitation of DNA polymerase: it's an extender, not a starter. It needs a "primer" to get started. The enzyme that makes this primer is appropriately named \textbf{Primase}.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question asks to identify the specific enzyme that creates the short RNA primers needed to initiate DNA synthesis during replication.
Step 2: Detailed Explanation:
Let's review the roles of the key enzymes in DNA replication:

Helicase: This enzyme unwinds the DNA double helix at the replication fork, separating the two strands to make them available as templates.
Primase: This is a type of RNA polymerase. Its specific job is to synthesize short RNA sequences, called primers (about 5-10 nucleotides long), that are complementary to the template DNA strand. DNA polymerase cannot start a new DNA strand from scratch; it can only add nucleotides to an existing 3'-OH group. The RNA primer provides this starting point.
DNA polymerase: This is the main enzyme of replication. It adds deoxynucleotides to the 3' end of the RNA primer, synthesizing the new DNA strand. It also has roles in proofreading and replacing the RNA primers with DNA.
Topoisomerase (or DNA gyrase in bacteria): This enzyme relieves the torsional strain and supercoiling that builds up ahead of the replication fork as the DNA unwinds.
Step 3: Final Answer:
The enzyme specifically responsible for synthesizing the RNA primers is Primase.