Comparison Table: DNA Replication vs Transcription
| Feature | DNA Replication | Transcription |
|---|---|---|
| Template | Both DNA strands | One DNA strand |
| Enzyme | DNA polymerase III (main) | RNA polymerase |
| Primer needed | YES (RNA primer from primase) | NO (initiates de novo) |
| Product | Two identical daughter DNA molecules | RNA (mRNA, tRNA, rRNA, etc.) |
| Direction of synthesis | 5'→3' | 5'→3' |
| Direction of template reading | 3'→5' | 3'→5' |
| New strand type | DNA | RNA |
| Starts at | Origin of replication (oriC) | Promoter |
| Ends at | When both forks meet (prokaryotes) | Termination sequence |
| Occurs in (euk) | Nucleus (S phase) | Nucleus |
| Processivity | High (continuous on leading strand) | Moderate |
| Error rate | ~1/10^7 (with proofreading) | ~1/10^4–10^5 (no proofreading) |
| Fidelity mechanism | 3'→5' exonuclease proofreading | No proofreading — RNA is transient |
Flow: Template → Product
Key Differences to Memorize for NEET:
- Only DNA replication needs a primer. Transcription does not.
- Replication copies ALL the DNA; transcription copies only specific genes.
- The product of replication is DNA; the product of transcription is RNA.
- DNA Pol synthesizes both strands simultaneously at a fork; RNA Pol transcribes only one strand at a time.
- Replication must be highly accurate (errors passed to daughter cells); transcription has higher error tolerance (RNA is temporary).