Lecture Notes: Transcription and Translation

Overview

• The lecture focuses on the molecular processes of transcription and translation, transforming DNA to RNA and using RNA to make proteins.

Transcription

• Steps in Transcription:
  • Initiation:
    • RNA polymerase binds DNA.
    • Requires a promoter sequence rich in A's and T's.
    • In prokaryotes, proteins are Sigma factors; in eukaryotes, they are transcription factors.
    • Eukaryotic genes have individual promoters; prokaryotic genes share promoters for functionally similar genes.
  • Elongation:
    • RNA polymerase adds nucleotides to the 3' end of the growing mRNA chain.
    • Uses complementary nucleotides from the nucleus.
    • RNA polymerases are prone to errors but do not require proofreading as RNA is transient.
  • Termination:
    • Specific sequences signal RNA polymerase to detach, completing mRNA transcript.
• RNA Processing in Eukaryotes:
  • Involves removal of non-coding regions (introns) and joining coding regions (exons).
  • RNA Splicing:
    • Small RNAs and proteins form a spliceosome.
    • Spliceosome cuts introns and joins exons.
  • Additional Structures:
    • 5' Cap: Methylated guanine is added for stability and protection.
    • Poly-A Tail: Provides a buffer against degradation.

Translation Preparation

• The processed mRNA exits the nucleus for translation. Further details on translation will be covered in subsequent lectures.

Key Points

• Transcription involves initiation, elongation, and termination.
• RNA polymerase finds a promoter with transcription factors in eukaryotes.
• RNA processing includes splicing and adding protective structures.
• Mature mRNA is prepared for translation.