[20.4] epigenetic control of gene expression Flashcards
1
Q
what is epigenetics?
A
heritable changes in gene function without changes to base sequence of DNA
2
Q
what is the epigenome?
A
chemical tags which cover DNA and histones which determine the shape of the DNA-histone complex
3
Q
what is epigenetic silencing?
A
when the epigenome keeps genes that are inactive in tightly packed arrangement so they cannot be read
4
Q
how does the epigenome switch on genes?
A
unwraps active genes so the DNA is exposed and can easily be transcribed
5
Q
what factors can the epigenome be afffected by?
A
environmental factors:
- diet
- stress
6
Q
how can environmental signals affect the DNA? (2)
A
- acetylation of histones leading to the activation or inhibition of a gene
- methylation of DNA by attracting enzymes that can add or remove methyl groups
7
Q
what is added during acetylation and methylation?
A
- acetylation - acetyl group is donated from acetylcoenzyme A
- methylation - methyl group added to cytosine bases of DNA
8
Q
what is the effect of decreased acetylation of associated histones?
A
- increased positive charge on histones
- increased attraction to phosphate groups of DNA
- association between DNA and histones is stronger
- DNA is not accessible to transcription factors
- transcription factors cannot initiatie mRNA production from DNA
- gene is switched off
9
Q
how can methylation inhibit the transcription of genes? (2)
A
- preventing the binding of transcriptional factors to the DNA
- attaching proteins that condense the DNA-histone complex by inducing deacetylation of the histones, making DNA inaccesible to transcription factors
