Protein Synthesis

From DNA to functional proteins: transcription, processing, and translation

Chapter Summary

Protein synthesis involves: (1) transcription of DNA into pre-mRNA, (2) processing of pre-mRNA (capping, polyadenylation, splicing), and (3) translation of mature mRNA into polypeptides. Multiple RNA types and enzymes ensure high fidelity and regulation.


Transcription

Transcription

RNA polymerase binds promoter, separates DNA strands, synthesizes pre-mRNA 5′→3′ using the template strand.

Key Enzymes & Mechanisms

  • RNA Polymerase II: synthesizes pre-mRNA in eukaryotes.
  • 5′ Capping: protects mRNA and aids ribosome binding.
  • Ribosome: decodes mRNA codons into amino acids.

Regulation & Clinical Correlations

  • Alternative Splicing: one gene → multiple proteins; mutations can cause disease (e.g., β-thalassemia).
  • Ribosomal Inhibitors: antibiotics like tetracycline block translation in bacteria.

Key Terms

Quiz Yourself

1. Which enzyme synthesizes pre-mRNA?

2. What modification protects mRNA from degradation?

3. In which organelle does translation occur?