12.2 feedback control of gene expression

Central Dogma and Feedback Loops

• The central dogma of molecular biology is updated with feedback mechanisms.

• McClintock's Feedback Loop: Introduces the idea of positive feedback from proteins back to DNA.

• Two Major Feedback Loops: These loops challenge the traditional view of the central dogma; they include both positive and negative feedback.

Oscillation in Gene Expression

• Notch Binding Protein: Important for embryogenesis; exhibited oscillatory gene expression with a two-hour cycle.

  • Fluctuation by a factor of four considered significant, but it occurs naturally every two hours.

• Oscillatory Responses: Caused by negative feedback loops, leading to periodic changes in gene expression.

Research Highlights

• Systems Biology at Harvard: Investigated the gene p53 and its oscillatory nature.

  • Found patterns of gene expression oscillating in a two to three-hour cycle (green leads pink).

• 2017 Nobel Prize: Recognized work on oscillations in biological systems, noting the role of time delays in feedback mechanisms.

Key Concept: Negative Feedback Loops

• Negative feedback from gene products inhibits the original producing gene, creating oscillatory patterns.

  • Example: The circadian rhythm is an outcome of such feedback loops.

• Revising the Central Dogma:

  • New model shows DNA to RNA to protein is influenced by feedback from proteins to DNA, indicating a complex interaction.

Conclusion

• The process of gene regulation is more complex than a simple command chain from DNA to RNA to protein.

• Proteins can influence DNA, highlighting a bidirectional flow of information and regulatory mechanisms.