In-Depth Notes on Gene Expression and Biopharming

Introduction to Gene Expression

• Gene expression converts specific genes into proteins, creating phenotypes from genotypes.
• Gene expression includes two main processes: transcription and translation.

Objectives of Chapter 10

• Explain how gene expression relates phenotype and genotype.
• Describe transcription and translation, identifying key steps and molecules involved.
• Understand the characteristics of the genetic code: unambiguous, redundant, universal.
• Define gene regulation and its significance.

Biopharming with Tobacco

• Biopharming: Manufacturing vaccine proteins in plants, specifically tobacco, by inserting genes into plant cells.
• Medicago, a biotechnology company, grows tobacco to produce influenza vaccines instead of traditional methods like using chicken eggs.
• Advantages of using plants include:
  • Rapid growth and scalability.
  • Cost-effectiveness compared to traditional vaccine production.
• First vaccine produced was for the H1N1 virus, synthesized from the hemagglutinin gene.

Gene Expression Process

Transcription

• Transcription: Process where RNA is synthesized from a DNA template.
• RNA Polymerase:
  • Binds to the promoter region of DNA.
  • Unzips DNA to expose the template strand.
  • Synthesizes mRNA using complementary RNA nucleotides (A-U, G-C).
  • Stops at terminator sequences.
• Modifications:
  • RNA ends are chemically modified; introns (non-coding sequences) are spliced out, exons (coding sequences) are joined together.

Translation

• Translation: Process where mRNA is decoded by ribosomes to form proteins.
• Essential RNAs involved:
  • Messenger RNA (mRNA): Carries genetic information from DNA.
  • Ribosomal RNA (rRNA): Forms part of the ribosome's structure.
  • Transfer RNA (tRNA): Transfers amino acids to ribosomes using anticodon pairing with mRNA codons.
• Codon Usage:
  • Ribosomes read mRNA in codons (three-base sequences).
  • There are 64 possible codons coding for 20 amino acids, indicating redundancy in the code.
• Start codon: AUG (Methionine); Stop codons: UAA, UAG, UGA.

Genetic Code Characteristics

• Unambiguous: Each codon maps to only one amino acid.
• Redundant: Some amino acids are coded by multiple codons.
• Universal: Genetic code is nearly identical across different organisms, supporting common descent.

Gene Regulation

• Gene Regulation: The ability to modulate gene expression in response to internal or external signals.
• Can modify:
  • Speed of transcription (up-regulation, down-regulation).
  • Allow organisms to adapt to environmental changes.
• Example in Medicago: Adjusting environmental factors (humidity, temperature) to optimize protein production in tobacco.

Conclusion & Clinical Applications

• Biopharming represents a significant efficiency improvement for vaccine production:
  • Medicago produced 10 million doses of flu vaccine in a month, while traditional methods could take 5–6 months.
  • Potential applications for other diseases, including rapid response to pandemics.

Important Questions

1. What are the advantages of biopharming over traditional vaccine production methods?
2. Describe the steps involved in transcription and the role of RNA polymerase.
3. Explain the significance of gene regulation in relation to gene expression and organism adaptation.