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Understanding Cancer Series

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  • Posted: 12/29/2009

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Slide 21

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Epigenetic Variation

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Reversible, heritable changes called epigenetic factors also can indirectly regulate gene expression and protein production. These modifications can occur even without a change (mutation) in a gene's DNA sequence. Epigenetic alterations may be induced spontaneously, in response to environmental factors, or may simply be part of a person's genetic background. Some examples include:

  • Addition of a methyl group to CpG dinucleotides, which are special regions in DNA bases where gene activity can be silenced when methyl groups are attached
  • Removal of acetyl groups from histone tails, which stops the gene activity of the DNA bases wrapped around the histone, causing the DNA to coil up tightly.
Graphic shows how gene activity is silenced when methyl groups are attached and when acetyl groups are removed from histone tails, gene activity stops, and the DNA coils up tightly.