8A Epigenic Control of Gene Expression Flashcards
What does epigenetic control do
Determines whether on not a gene is expressed
How are epigenetic changes inherited by offspring
Most epigenetic marks are removed some escape the removal process and are passed on by offspring
Define epigenetics
heritable changes in gene function without altering the base DNA sequence.
What is epigenetic changes caused by
Environmental factors/changes
How does increased methylation of DNA inhibit transcription
When a methyl group is added to the cytosine base on DNA this prevents RNA polymerase and transcription factors from binding and so the gene is not expressed
How does decreased acetylation of histones inhibit transcription
When acetyl groups are removed from the histones the chromatin becomes highly condensed and the genes in the DNA can’t be transcribed because transcription factors can’t access them
How does increased acetylation of histones stimulate transcription
When histones are acetylated chromatin is less condensed this means that RNA polymerase and transcription factors can reach the DNA allowing genes to be transcribed
Are epigenic changes fixed
No they are reversible
How do drugs prevent epigenetic changes
Some stop DNA methylation eg azacytidine is used in chemotherapy
HDAC inhibitor drugs work by inhibiting the activity of histone deacetylase enzymes which are responsible for removing acetyl groups from the histones so the genes remain acetylated and the proteins they code for can be transcribed
