Lecture Notes: Central Dogma of Molecular Biology

Key Concepts

• Central Dogma: DNA → RNA → Protein

Transcription Process

1. Initiation of Transcription:

   • Transcription factors assemble at a specific promoter region along the DNA.
   • Gene Definition: Length of DNA following the promoter which contains the recipe for a protein.

2. Transcription Initiation Complex Formation:

   • Involves a mediator protein complex carrying RNA polymerase.
   • RNA polymerase is maneuvered into place with the help of other factors.
   • Collection of all factors is called the transcription initiation complex.

3. Activation of the Initiation Complex:

   • Activator proteins bind to enhancer regions (specific DNA sequences).
   • Enhancer regions can be thousands of base pairs away from the gene start.
   • Contact between activator proteins and the initiation complex releases the copying mechanism.

Mechanism of RNA Synthesis

• RNA Polymerase Function:

  • Unzips a portion of the DNA helix, exposing bases on each strand.
  • Only one DNA strand is copied; serves as a template for RNA synthesis.

• Formation of RNA Molecule:

  • RNA is synthesized by matching DNA letter code on the template strand.
  • Sub-units enter the enzyme through an intake hole and are joined to form long messenger RNA chains.

Important Structures

• Promoter Region: Initial binding site for transcription factors.
• Transcription Initiation Complex: Assembled collection of proteins and factors facilitating transcription.
• Enhancer Regions: DNA sequences that are binding sites for activator proteins.

Summary

• The process of transcription is initiated by the assembly of transcription factors at the promoter region.
• RNA polymerase is directed into place by a mediator protein complex, forming the transcription initiation complex.
• Activation requires binding of activator proteins to enhancer regions, releasing RNA polymerase to synthesize RNA.
• RNA synthesis involves copying one DNA strand to form a messenger RNA molecule, which is then used in protein synthesis.