An answer to the question:

"Why are some genes expressed and not others?"

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The Learn.Genetics Epigenetics module explores some of the mechanisms responsible for the differential expression of genes, and how environmental factors influence those mechanisms. As an organism grows and develops, carefully orchestrated chemical reactions activate and deactivate parts of the genome at strategic times and in specific locations. Epigenetics is the study of these chemical reactions and the factors that influence them.

DNA & Histone Model

A 3-D cut-and-paste model depicting how histone, acetyl and methyl molecules control access to DNA and affect gene expression. Can be used as a companion to, or in place of, the Gene Control interactive.

Tip: With the epigenome-specific instructions and molecule models removed, these print-outs can be used to create general chromosome models. Modify the model further by copying the DNA strips (page 7) on to help model recombination (crossing over) during meiosis.

Learning Objectives
  • DNA is coiled around histones.
  • Tightly coiled DNA is inaccessible to gene reading machinery.
  • Methyl molecules bind to DNA and block access to genes.
  • Acetyl molecules bind to histones and improve access to genes.

DNA Histone Model (PDF)

DNA Histone Model (Tutorial video)

Your Environment, Your Epigenome

Using a checklist, students record some of the epigenome-influencing factors present in their environments.

Learning Objectives
  • Factors from your environment such as diet, physical activity, and stress influence the epigenome.

Download Print-and Go (PDF)

Epigenetics Science Talk

The Epigenome As an Interface Between the Social Environment and Our Genome

Moshe Szyf Ph.D.
Department of Pharmacology and Therapeutics,
McGill University, Montreal Canada

Talk given in Summer of 2008 during the Beyond the Central Dogma Summer Institute at the Genetic Science Learning Center

Watch Video

Sample Assessment Questions


Funding for this project was provided by a Science Education Partnership Award from the National Center for Research Resources, a component of the National Institutes of Health.