Lecture Notes: Epigenetics and the Differences in Identical Twins

Introduction

• Identical twins originate from the same DNA but can develop differently.
• Differences can be found in traits with a significant genetic component.
• Example: One twin having heart disease and another in perfect health.

Nature vs. Nurture

• Nature vs. nurture plays a role in differences.
• Epigenetics provides a deeper explanation for these differences.

What is Epigenetics?

• Study of how DNA interacts with smaller molecules in cells that activate/deactivate genes.
• DNA is like a recipe book; molecules determine what gets expressed.
• Molecules' presence within cells makes the difference, not conscious choices.

Gene Expression and Proteins

• Genes expressed when read and transcribed into RNA.
• RNA translated into proteins by ribosomes.
• Proteins determine cell characteristics and function.
• Epigenetic changes influence transcription of specific genes.

Mechanism of Epigenetic Changes

• DNA/proteins wrapped around it can be labeled with chemical tags.
• Epigenome: Set of all chemical tags on a cell's genome.
• Methyl groups: Inhibit gene expression by affecting transcription machinery or DNA coiling.
• Tags can also unwind DNA, boosting transcription.
• Epigenetic changes can persist through cell division, affecting the organism's lifespan.

Role in Development

• Epigenetic changes are part of normal development (e.g., cell differentiation in embryos).
• Approximately 200 cell types have the same genome but distinct epigenomes.

Environmental Influence

• Diet, chemical exposure, medication influence epigenetic changes.
• Changes can lead to diseases if they affect tumor-suppressing genes.
• Identical twins: Diverging epigenomes affect aging and disease susceptibility.
• Social experiences: Affect epigenetic changes (e.g., mother rats' attentiveness affecting pups).

Inheritance of Epigenetic Marks

• Most marks erased in egg/sperm formation, but some might survive.
• Parents' experiences/choices can influence offspring epigenome.

Reversibility and Health

• Epigenetic changes aren't necessarily permanent.
• Balanced lifestyle could promote a healthy epigenome.

Future of Epigenetic Research

• Understanding mechanisms of human development, aging, disease origins.
• New genome editing techniques identify important epigenetic changes.
• Potential for influencing the epigenome for better health outcomes.

Key Takeaways

• Epigenetics offers insights into how identical twins can differ despite identical DNA.
• Environmental factors significantly influence gene expression beyond just genetic coding.
• Lifelong effects and potential reversibility of epigenetic changes are areas of active research.