topic 8 epigenetics Flashcards
what does epigentic control determine?
whether a gene can be expressed or not
how do epigenetics determine whether a gene can be expressed or not?
attaches or removes epigenetic marks to/from DNA or histone proteins
what are epigenetic marks?
chemical groups
do epigenetic marks alter the base sequence of DNA?
no
what do epigenetic marks do?
alter how easy it is for enzymes/proteins needed for transcription to interact and combine with DNA
what role do epigenetic markers have?
play a role in normal cell processes and can occur in response to enviornmental changes
what do organisms inherit from their parents?
DNA base sequences
are genetic marks passed on between generations?
most removed but some may remain
what can expression of genes be affected by?
environmental changes
what are examples of epigenetic control?
increased methylation of DNA
decreased acetylation of histones
how does increased methylation of DNA affect epigenetic control?
methyl group attached to DNA coding for a gene
group attaches at the CpG site- where cytosine and guanine bases are adjacent
increased methylation changes the DNA structure so transcriptional machninery cannot interact with the gene
gene is not expressed
how does decreased acetylation of histones affect epigentic control?
histones can be more or less condensed
this affects how accessible DNA is and whether or not it can be transcribed
what happens when histones are acetylated?
chromatin is less condensed
transcriptional machinery can access DNA
so genes can be transcribed
what happens when acetyl groups are removed from histones?
chromatin is highly condensed
genes can’t be transcribed as transcriptional machinery can’t access them
what enzymes are responsible for removing acetyl groups?
histone deacetylase
what enzymes are responsible for removing acetyl groups?
histone deacetylase
what can epigenetics lead to?
the development of disease
what is Fragile X disorder?
genetic disorder that leads to learning/behavioural difficulties
what is Fragile X disorder caused by?
heritable duplication on gene on the X chromosome
short DNA sequence CGG repeated
so more CpG sites in the gene than usual
more CpG sites= increased methylation of gene- switches it off
protein that it codes for is not produced
lack of protein causes symptoms of the disease
what can be used to treat diseases caused by epigenetic changes?
drugs
how can drugs be used to treat diseases caused by increased methylation?
drugs stop DNA methylation
eg) drugs used in chemotherapy for types of cancer caused by increased methylation of tumour suppressor genes
how can drugs be used to treated diseases caused by decreased acetylation of histones?
HDAC inhibitor drugs inhibit the activity of histone deacetylase enzymes, which remove the acetyl groups from histones
without the activity of HDAC enzymes, the genes remain acetylated and the proteins they code for can be transcribed
what is it imporant for drugs to be if they are used to treat diseases caused by epigenetic changes?
specific
