epigenetics and gene expression Flashcards
in eukaryotic organisms, give one process controlled by epigenetics ?
- gene expression in protein synthesis
- so when a protein is made
what is meant by epigenetics ?
- the heritable change in gene function (preventing gene expression)
- without changing the DNA sequence
what are heritable changes in gene function caused by ?
- changes in the environment
what can heritable changes inhibit ?
- they can inhibit transcription
what kind of environmental factors can cause heritable changes ?
- diet
- stress
- toxins
what can the environmental factors do to the DNA to cause heritable changes ?
- they can add or remove epigenetic chemical tags to the DNA
- and this can control gene expression in eukaryotes
what is the single layer of chemical tags on the DNA called ?
- epigenome
what does the epigenome impact ?
- this impacts the shape of the DNA-histone complex
- and whether the DNA is tightly wound so won’t be expressed or unwound so it will be expressed
what happens if the histone is tightly wound around the DNA ?
- DNA will not be expressed
- transcription factors cannot bind
-so epigenome, which is due to changes in the environment, can inhibit transcription
will the DNA be expressed if the histone is unwound ?
- yes
- it will be expressed
- as genes are accessible to be transcribed
what are the 3 types of chemical tags ?
- methylation of DNA
- acetylation of histone proteins
what is meant by methylation of DNA ?
- when methyl groups are added to the DNA
what does increased methylation of DNA do ?
- it inhibits transcription
where do the methyl groups attatch to ?
the cytosine base
how does increased methylation inhibit transcription ?
- by binding onto cytosine bases
- it prevents transcriptional factors from binding
- and attracts proteins that condense the DNA -histone complex
- so it prevents a section of DNA from being transcribed
how does methylation make the DNA more compact ?
- methyl groups are positively charges
- DNA is negatively charged
- so the strong attraction between opposite charges causes them to become compact
what does decreased acetylation of associated histone proteins on DNA do ?
- it inhibits transcription
what occurs when the acetyl groups are removed from the DNA ?
- the histones become more positive and are attracted more to the phosphate group on the DNA
- this makes the DNA and histones more strongly associated and hard for transcription factors to bind
where are acetyl groups binded to ?
- the histones
what does increased acetylation cause ?
- histones to become loosely packed
- so transcription factors can bind to the DNA and genes can be expressed
what is the term given when the DNA is tightly coiled ?
- heterochromatin
what is the term given when the DNA is loosely coiled ?
- euchromatin
what is heterochromatin caused by ?
- increased methylation
- decreased acetylation
what is euchromatin caused by ?
- decreased methylation
- increased acetylation
what are tumour suppressor genes ?
- genes that produce proteins to slow down cell division
- and to cause cell death if DNA copying errors are detected
what occurs if a mutation results in a tumour suppressor gene not producing the proteins to carry out its function ?
- the cell division could continue
- mutated cells would not be identified and destroyed
what are the 2 known mutated tumour suppressor genes that are linked to breast cancer ?
- BRCA1
- BRCA2
what can methylation cause a gene to do ?
- can cause a gene to be turned off or on
what can happen to tumour suppressor genes in terms of methylation ?
they could become hypermethylated
what does the hypermethylation of tumour suppressor genes result in ?
- an increased number of methyl groups become attatched to it
- coiling it up
- resulting in genes being inactivated and become turned off
- so you can get uncontrolled cell division
what can occur in oncogenes in terms of methylation ?
- they can become hypomethylated
what occurs when oncogenes are hypomethylated ?
- it reduces the number of methyl groups attached to it
- causing it to unwravel
- which results in the gene being permanently switched on
- oncogenes create proteins which trigger mitosis to occur
- so this will result in uncontrolled mitosis and cell division
