Biology Lecture: The Depths and Complexities of Genetics and Epigenetics

Introduction

• Depth and complexity: Many traits are more complex than initially thought (e.g., eye color).
• Polygenic traits: Multiple genes involved in traits previously considered simple (e.g., earlobes).
• Continuous discovery: The field of biology is vast with new discoveries ongoing.

Punnett Squares and Complex Traits

• Initially taught as simple genetic tools for traits like eye color.
• Eye color: A polygenic trait, more complex than represented by Punnett squares.
• Other traits (e.g., earlobes): More complex than initially taught.

Epigenetics

• Definition: Study of changes in gene expression not caused by changes in the DNA sequence.
• Significance: Explains differences between identical twins in traits and diseases.
• DNA Bases: Code for physical traits but affected by epigenetic factors.

Epigenetic Marks

1. Methylation: DNA and Histones
   • Methyl groups attached to DNA bases prevent transcription.
   • Histone methylation: Prevents transcription by impacting histone-DNA interaction.
2. Histone Acetylation and Deacetylation
   • Acetylation: Attaches acetyl groups, making DNA wrapping loose, enabling transcription.
   • Deacetylation: Removes acetyl groups, tightening DNA around histones, limiting access to transcription machinery.

Examples in Rodents

• GR Gene in Rats: Parental care (e.g., licking and grooming) affects stress response gene expression via epigenetic marks.
• Agouti Gene in Mice: Affects coat color and obesity; environmental factors during pregnancy can impact gene expression.

Inheritance of Epigenetic Marks

• Mitosis: Daughter cells can inherit epigenetic marks from original cells.
• Reproduction: Some epigenetic marks are cleared in gamete creation, but some can be inherited from parents.

Internal and External Cues

• Internal cues: Specialized cells transcribing specific genes (e.g., eye cells vs. stomach cells).
• External Environment: Can influence epigenetic marks (e.g., diet, behavior).

Importance of Epigenetics

• Medical relevance: Understanding diseases with genetic components (e.g., cancer) involves epigenetics.
• Epigenetic therapy: A promising field for treating medical conditions by targeting epigenetic marks.
• Understanding the epigenome: Essential for better understanding of cellular function and disease.

Conclusion

• Continuous learning: Encouragement to explore and stay curious about the complexities of biology.