What is epigenetics?
changes in gene expression, usually caused by a change in the environment
What is meant by the term ‘epigenome’?
all of the chemical tags on the DNA of an organism
Why is DNA not transcribed when methyl groups are bound?
As transcription factors cannot bind
What is methylation?
adding on a methyl group
Where do methyl groups attach to DNA?
on the Cytosine base
What does increased methylation result in?
less transcription so less gene expression
why does increased methylation reduce transcription?
- methyl groups prevent transcription factors from binding
- methyl causes proteins which increase deacetylation, reducing gene expression
What is acetylation?
the addition of acetyl groups to the histones
What does DECREASED acetylation result in?
inhibited transcription
Why does increased acetylation result in increased transcription?
histones become neutral, so sections of DNA exposed therefore transcription factors can bind
What makes the DNA negatively charged?
phosphate groups
Describe deacetylation and its impact on gene expression…
- acetyl groups are removed from histones
- causes the histones to become positively charged
- negatively charged phosphate groups are attracted to the positively charged histones
- DNA becomes more tightly coiled
- so transcription factors cannot bind so the gene is not expressed
What adds and removes epigenetic tags?
enzymes
