8. Epigentic Control Of Gene Expression Flashcards
What 2 factors control gene expression ?
Transcription factors
Epigenetic changes
Epigentic Contol in eukaryotes ?
Determine whether a gene is switched on or off ( whether gene is expressed -transcribed&translated) or not.
Works through attachment of removal of chemical groups called epigenetic markers to form dna or histone protein
They alter how easy it is for an enzyme and other proteins needed for transcription to interact with and transcribe dna
Inheriting epigenetic changes
Most are removers between generations but some escape removal and passed to offspring
Do expression of some genes in offspring can he affected by environmental changes tha affected their parents / grandparents
Increased methylation of dna
Group attached for CpG site which is where a cytosine and guanine base are next to eachother in dna
Increased methalydayon changes dna structure so that the trascriptional machinery can’t interact with gene so gene switched off
What methyl group is attached to cytosine by enzymes called, what ?
Methyltransferases
Decreases acetylation of histones
When histones are acetylated the chromatin is less condensed meaning transcriptional machinery can access the DNA allowing genes to be transcribed
When acetyl groups are removed from histones the chromatic becomes highly condensed and genes in dna can’t be transcribed because transcriptional machinery can’t physically get to dna
What are histone proteins ?
Dna wraps around them to form chromatic which makes chromosomes
Chromatin can be highly condensed or less condensed ehich will affect the accessibility of the dna and weather or not it can be transcribed
They can be epigenetic ally modified by addition or removal or acetyl groups
What is an acetyl group?
-COCH3
What is a methyl group ?
-CH3
What types of diseases can epigenetics play a role in ?
Fragile X syndrome
Angelman syndrome
Prayer William syndrome
How are epigenetic changes better / easier to treat then dna mutations ?
Reversible
Good targets for new drugs to combat disease
Drugs xountrrfact epigenetic changes causing diseases
Drugs in chemotherapy
Used for types of cancers that caused by increased methylation of tumour aupressor genes
Tumour suppressor genes slow down divsion so if they’re switched off by methylation cells can divide uncontrollably forming tumour
The drugs inihibuts methylation of genes by physically blocking the enzymes involved
Treating decreased acetylation
HDAC inhibitor drugs used to treat diseases that are caused this way - cancers
Inhibiting the activity of histone deaceylasde eneyzkes ehich are responsive for removing acetyl groups from histone
Without activity of HDAC enzymes genes remaine acetylated and proteins they code for can be transcribed
Problem with developing drugs to counteract epigenetic changes ?
Important drugs are species as possible
Also could activate transcription in normal cells - cancerous which creates problem that was supposed to be stopped
