The on-off switch
Epigenetics: Choosing the Adventure

June 1, 2015

The genome is often described as a blueprint or a recipe – a step-by-step set of instructions for creating a living thing. But, in reality, these instructions are more dynamic than that – more like a choose-your-own-adventure book than a set of steps that must be followed in sequence. While the genetic code itself is essentially unchangeable, the way in which it gets read and acted upon can change.

The field of epigenetics – meaning "above" genetics – explores how environmental factors, such as nutrition and stress, create long-term changes in gene activity. Epigenetic changes are molecular tags that attach themselves to the genome without changing the DNA code. These tags serve as notes, telling a cell whether or not to read a gene. An epigenetic tag can determine which sentences are magnified, or which pages of the book are open at a given time.

So far, researchers have focused on studying a few types of epigenetic change, particularly a process known as methylation, in which small molecules called methyl groups bind with DNA or the proteins that package DNA, altering gene activity. Researchers are just beginning to understand how these changes impact our health. For example, cancer researchers are trying to determine the role that epigenetic changes might play in switching on and off the genes that can turn a healthy cell into a cancerous one. Other researchers are exploring how stress during critical periods in development can affect a child's risk of developing a range of illnesses, from depression to diabetes, later in life.

As the Government of Canada's health research investment agency, the Canadian Institutes of Health Research (CIHR) sets strategic priorities to respond to key health and health system challenges. In this issue of Show me the Evidence, we profile the Canadian Epigenetics, Environment and Health Research Consortium (CEEHRC), a Signature Initiative to support leading-edge research on the role of DNA and environment interactions in human health and disease. CIHR's Signature Initiatives capitalize on Canada's research strengths and help us make strategic investments in promising areas of health research.

The CIHR-supported research highlighted in this issue has not only helped improve our understanding of epigenetics, it's also laying the foundation for improvements in diagnosis and treatment of a wide range of diseases. The stories describe:


Chemical probe – A small molecule that has been designed to interact with a specific protein, so that researchers can better understand the protein's function.

Chromatin – Within a cell, DNA molecules are tightly wrapped around proteins. This condensed DNA-protein structure is called chromatin, and it makes up chromosomes.

Chromosome – The DNA in a cell is divided into structures called chromosomes. Different species have different numbers of chromosomes. For example, humans have two sets of 23 chromosomes (with one set inherited from each parent).

DNA – Short for deoxyribonucleic acid, DNA is a very long molecule that contains biological information and transmits this information from one generation to the next in living things. It consists of a code that provides instructions for the structures and processes necessary for life. Your DNA sequence is unique to you (unless you have an identical twin).

Epigenetics – This field of scientific study explores how environmental factors create long-term changes in gene activity.

Epigenomics – The study of all the epigenetic modifications in a genome.

Gene – A gene is a stretch of DNA sequence with a specific function. In general, a gene contains the code for a protein, which has a defined role in the body.

Genetics is the study of genes and how they work.

Gene expression – Genes aren't active all the time. When a cell is making a protein based on the instructions contained in a gene, scientists say the gene is being “expressed.”

Genome – Genome is the term for an organism's complete genetic material. For example, an individual human genome is all of the genetic information contained in a person's 23 pairs of chromosomes. Genomics is the study of the information contained in the genome.

Methylation – This is a type of chemical reaction in which a small molecule, known as a methyl group, is attached to a DNA strand or a histone protein. These chemical changes are epigenetic modifications that can increase or decrease the activity of a gene.

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