Question

D polymerase $\delta$ in eukaryotes is involved in:

• A. Synthesis of R primer
• B. Replication of mitochondrial D
• C. Replication on the leading strand of D
• D. Replication on the lagging strand of D

Hint:

Eukaryotic Replicative Polymerases:
Pol $\alpha$ = Initiates Primase.
Pol $\epsilon$ = Leading strand synthesis.
Pol $\delta$ = Lagging strand synthesis.
Pol $\gamma$ = Mitochondrial D replication.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for the primary physiological role of eukaryotic D polymerase delta ($\text{Pol } \delta$) during nuclear D replication.

Step 2: Key Formula or Approach:
Eukaryotic nuclear D replication utilizes three main replicative D polymerases:
• Pol $\alpha$ Primase: Synthesizes R primers and short initiator D stretches.

• Pol $\epsilon$: Primary enzyme responsible for continuous leading strand elongation.

• Pol $\delta$: Primary enzyme responsible for discontinuous lagging strand elongation and Okazaki fragment processing.

• Pol $\gamma$: Replicates mitochondrial D.

Step 3: Detailed Explation:

• Function of D Polymerase $\delta$: D polymerase $\delta$ is a multi-subunit complex possessing high processivity when bound to Proliferating Cell Nuclear Antigen (PC). It carries out synthesis of Okazaki fragments on the lagging strand during nuclear D replication.

• Proofreading and Repair: Pol $\delta$ contains intrinsic $3' \to 5'$ exonuclease activity for proofreading and plays essential roles in nucleotide excision repair and mismatch repair.

• Evaluation of Other Options:
• Synthesis of R primer: Performed by the primase subunit associated with Pol $\alpha$.

• Replication of mitochondrial D: Carried out specifically by D Polymerase $\gamma$ ($\text{Pol } \gamma$).

• Leading Strand Replication: Primarily executed by D Polymerase $\epsilon$ ($\text{Pol } \epsilon$).

Step 4: Fil Answer:
D polymerase $\delta$ is predomintly involved in synthesizing the lagging strand during eukaryotic nuclear replication.