1. Epigenetic modification of DNA
Methylation is the gradual addition of chemical units known as methyl groups to genes, and as these groups accumulate, the gene gradually shuts down.

2. DNA methylation is the addition of a methyl group to the carbon-5 position of cytosine residues.

3. Epigentics webcast Webcast - 11/28/2007 - The Burrill Report
Alterations in DNA methylation are regarded as epigenetic and not genetic changes, because they do not materially affect the genetic code.

4. The Human Epigenome Project (HEP)
aims to identify, catalogue and interpret genome-wide DNA methylation patterns of all human genes in all major tissues.
Methylation is tissue specific and is of major importance in the regulation of gene expression during development.

5. Methylation is the only flexible genomic alteration which can change the way the genome functions under exogenous influence.
It constitutes the main, and so far missing, link between genetics, disease and the environment that is widely thought to play a decisive role in the development of virtually all human pathologies.

6. cancer
The human body is prone to developing cancer, from a very early stage of life, until the end of life.
The human genome has several built in tumour suppressor genes, whose protein products suppress the formation of tumours. It is important for these genes to continue expressing their tumour suppressor proteins as long as the person lives.
One way these genes can lose their ability to make protective proteins is through methylation.

7. One way these genes can lose their ability to make protective proteins is through methylation.
The pattern of methylation observed in cancer generally shows a dramatic shift compared with that of normal tissue.

8. Dolly (1996-2003) The first cloned mammal
Inefficient reprogramming of epigenetic marks is the main reason for the poor health of cloned animals.

9. Human Epigenome Project
One of the aims of the Human Epigenome Project (HEP) is to generate tissue-specific DNA methylation reference profiles of the human genome.
The chosen approach involves treatment of the genomic DNA with sodium bisulphite which converts unmethylated cytosines into uracil but does not affect methylated cytosines. Following PCR amplification and sequencing of selected amplicons from bisulphite-converted DNA, the degree of methylation can be determined by comparison of the corresponding signal ratios at CpG dinucleotides, the predominant sites of DNA methylation.