Question

In E.coli, the enzymatic product of dnaG gene required for the synthesis of ________.

• A. Leading strand DNA
• B. RNA Primer
• C. Okazaki fragments
• D. Lagging stand DNA

Hint:

Remember the key replication proteins in E. coli:
- dnaG encodes Primase (synthesizes RNA primers).
- dnaB encodes Helicase (unwinds the DNA duplex).
- dnaA encodes the Initiator protein (binds to the origin of replication, oriC).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
DNA polymerases cannot initiate DNA synthesis de novo; they require a free 3'-hydroxyl (\(-\text{OH}\)) group to begin adding nucleotides.
This initial 3'-OH group is provided by a short segment of RNA.

Step 2: Detailed Explanation:
In E. coli, the dnaG gene encodes the enzyme DNA Primase.
The direct enzymatic product of DNA Primase is the short RNA Primer.
While a single RNA primer is sufficient to initiate continuous synthesis on the leading strand, the replication of the lagging strand is discontinuous.
The lagging strand must be synthesized in short segments called Okazaki fragments.
Each Okazaki fragment requires the synthesis of a new RNA primer by the DnaG primase.
Because of this discontinuous mechanism, the active and continuous production of these RNA primers by the DnaG gene product is a mandatory requirement for the synthesis and elongation of the entire lagging strand DNA (D) (spelled "Lagging stand DNA" in the question paper).
Without DnaG primase activity, lagging strand synthesis is completely blocked, making the gene product essential for lagging strand replication.

Step 3: Final Answer:
In E. coli, the product of the dnaG gene is required for the synthesis of Lagging strand DNA.