Topic 8- Epigenetics Flashcards
What do Epigenetics involve?
changes in gene function, without changes to the base sequence of DNA
What is the epigenome?
All of the chemical modifications to all histone proteins and DNA (except base changes) in an organism
How can histobne proteins be chemically modified?
addition of acetyl
How can DNA be chemically modified withoutr changes to the base sequence?
addition of methyl groups
Is the epigenome heritable but also subject to change?
Yes
What are changes to the epigenome linked to? Give some examples?
-Changes to the environment
-Smoking, stress, exercise and diet
-Internal signalling from the body’s own cells
What does the chemical modification of histones and DNA control?
-How tightly DNA is wrapped around histones because there is changes to intermolecular bonding between them
What happens if DNA is wrapped more tightly around the histone? Why?
-Genes in this section of DNA are switched off
-The gene and promoter regions are more hidden from transcription factors and RNA polymerase
The 1._______ of histones is 2._____ and therefore can be 3.______ in different 4.____ types and can 5.____ with age
1.modification
2.reversible
3.different
4.cell
5.vary
Where can acetyl groups be added?
to lysine amino acids on histone proteins
What are the properties of lysine?
-Positivley charged R groups
-Forms ionic bonds with negatively charged phosphate backbone of DNA
Why does adding acetyl make DNA less tightly wrapped?
-It removes the positive ion
-Removes bond between histone and DNA
Why does acteyl stimulate gene expression?
-DNA is less tightly wrapped
-RNA polymerase and transcription factors can bind more easily
What does deacetylation cause?
-Lysine returns to a positivley charged state
-Has a stronger attraction to the DNA molecule, inhibits transcription
Where are mythel groups added?
Carbon molecule on cytosine bases (within sequnces that have multiple cytosine and guanine bases)
What does the addition of mythel groups cause? Why?
-suppresses the transcription of the affected gene
-the methylated bases attract proteins that bind to the DNA and inhibit transcription
