Epigenetics Flashcards
What is the definition of epigenetics?
Heritable changes in gene expression that are not a consequence of changes in DNA sequence.
What is the importance of epigenetics?
Allows daughter cells to retain identity during division.
Why is it important to study epigenetics?
Can be modified, environmentally and pharmacologically.
Can prevent ageing.
What are the 2 epigenetic marks?
- DNA methylation
- Histone modifications
What is DNA methylation?
Addition of a methyl group.
Where does methylation take place?
Only at cytosine
Why is methylation important in epigenetics?
Only commonly occurring covalent modification of DNA.
Which site on cytosine does methylation occur at?
5
What enzymes are involved in methylation of cytosine?
DNMT 1, 3a and 3b.
What class is DNMT1?
Maintenance, methylation pathways can be inherited when they divide.
What class are DNMT 3a and b?
Noval, add methylation to DNA which previously wasn’t.
What is SAM?
Universal methylation doner, acts as a co-factor.
What kinds of cytosines are methylated?
CPG dinucleotides.
What are CpG dinucleotide?
Cytosine that precedes a guanine.
Hoe many of the CpG sites in the genome are methylated?
70%
What are CpG islands?
Areas of the genome which have higher CpG sites.
What is the importance of methylation in repetitive regions?
Keeps gene expression off.
Suppression of “invading” DNA.
Suppression of inappropriate transcription.
What is the importance of methylation on the genome?
Transcription factors can’t bind so those genes are not expressed.
How many CpGs are there within the genome?
Genome is very CpG poor.
Where are CpG islands?
Within promotor regions.
How many active X chromosomes do women have?
1
How is the other X chromosome made inactive.
Methylation .
Why is it important we have only 1 functioning X chromosome?
Because it prevents over expression of genes.
What are imprinted genes?
Genes whose expression is determined by the parent that contributed to them.
What is the function methylation mostly?
Attracts huge protein complexes which change histone position and represses gene expression because transcription factors cannot bind.
Can methylation occur at different places?
Yes, CpA CpT CpC.
What is hydroxy methylation?
The start of demethylation but not common as it can cause cancer.
What kinds of histone modifications are there?
– Acetylation
– Methylation
– Phosphorylation
– Ubiquitination
Where does the histone modification take place?
On their funky little tails.
What happens when acetylation occurs on the histone?
Activation
Decompaction
DNA becomes permissive
What happens when methylation occurs on the histone? K9 – H3 and K27 – H3
Inactivation
Compaction
Non-Permissive
What is epigenetic drift?
The accuracy of which is DNA is methylated is much lower than DNA replication.
What happens to DNA methylation with age?
DNA methylation pattern breaks down, reduction of CpG islands which leads to incorrect cell function.
What is frailty?
Can be defined as a syndrome of decreased
reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems and causing vulnerability to adverse outcomes.
What is the importance of methylation for frailty?
The more methylation you have the less frailty you have.
Can methylation be used to predict age?
Clear correlation gives an indication of age based on methylation.
BUT only biological age.
What can happen when you get abnormal methylation?
You become more prone to developing cancer.
Why is DNA methylation important in regards to ageing?
If you prevent methylation you can sometimes prevent age-related diseases.
What are HATs?
Histone acetyltransferase
