Epigenetics

Introduction to Epigenetics

• Definition: Epigenetics studies how environmental and developmental factors affect gene expression and its implications for human health.

• Key Concept: Nucleosomes, made up of DNA and histone proteins, can block RNA polymerase II from binding to DNA, thus affecting transcription.

Learning Outcomes

Understanding Chromatin

• Each chromatin molecule consists of a DNA molecule and histone proteins.

• Storing DNA in chromatin form benefits cell function.

Epigenetic Changes

• Definition: Dissemination of biological changes due to environmental factors.

• Result from changes in chromatin structures through chemical modifications, which can be reversible and inherited.

Chemical Modifications

• Key Modifications:

  • Acetylation: Addition of acetyl groups to histones makes DNA available for transcription.

  • Methylation: Addition of methyl groups to cytosine in DNA affects gene expression.

  • Modifications enable response to environmental factors like stress, nutrition, toxins.

• Epigenetic inheritance involves trait transmission without altering nucleotide sequences.

Impact of Epigenetics on Health

Environmental Effects

• Epigenetic changes can acclimate individuals to their surroundings and potentially affect health risks related to various diseases (e.g., cancer, diabetes).

• They change the risk of aging and phenotype variances among genetically identical individuals.

Chromatin Structure and Gene Expression

Relationship Between Nucleosomes and Chromatin

• Nucleosomes are the building blocks of chromatin.

• Chromatin density influences gene activation:

  • Tightly-packed regions: Inaccessible and repressed genes.

  • Loosely-packed regions: Accessible and expressed genes.

Response to Environmental Factors

• Changes in environmental factors lead to chromatin structure adjustments, influencing gene transcription without altering the DNA sequence.

• The biology of the cell adjusts, changing health risk profiles.

Nutrition's Role in Epigenetics

• Excess caloric intake represses specific genes (e.g., Gene Z), increasing disease risk.

• Reduced caloric intake may express these genes, reducing risks.

Epigenetics and Adaptation

• Epigenetic alterations facilitate acclimation to environmental changes, influencing stress responses.

• Information about current environments is passed from parents to offspring providing adaptive advantages.

Phenotype Variation

• Identical individuals exhibit phenotype variance due to differing environmental influences, such as nutrient availability, sensory stimulation, and social interactions.

Lifelong Impact of Epigenetics

• Epigenetic changes occur throughout life, affecting health and disease risks.

• They correlate with factors like obesity and chronic diseases.

Epigenetics and Cells

• As environmental conditions fluctuate, cells adjust gene expression to produce proteins necessary for adaptation affecting overall health.

Emotional and Nutritional Factors

• Emotional stress and excessive caloric intake lead to increased health risks, including depression and Type II diabetes.

Intergenerational Epigenetic Transmission

• Parents can transmit acquired epigenetic changes through gametes, influencing the health of offspring by exposing them to varied environmental experiences during pregnancy.

Study Guide Questions

• Identify biological molecules forming chromatin in the nucleus.

• Define nucleosome and assess environmental impacts on chromatin structure and gene expression.

• Investigate epigenetic changes in relation to mutations and external factors.

• Examine how lifestyle adjustments could induce beneficial epigenetic changes for health improvement.