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Biology Of Ageing Year2 > Epigenetics > Flashcards

Epigenetics Flashcards

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1
Q

What is the definition of epigenetics?

A

Heritable changes in gene expression that are not a consequence of changes in DNA sequence.

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2
Q

What is the importance of epigenetics?

A

Allows daughter cells to retain identity during division.

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3
Q

Why is it important to study epigenetics?

A

Can be modified, environmentally and pharmacologically.
Can prevent ageing.

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4
Q

What are the 2 epigenetic marks?

A
  • DNA methylation
  • Histone modifications
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5
Q

What is DNA methylation?

A

Addition of a methyl group.

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6
Q

Where does methylation take place?

A

Only at cytosine

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7
Q

Why is methylation important in epigenetics?

A

Only commonly occurring covalent modification of DNA.

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8
Q

Which site on cytosine does methylation occur at?

A

5

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9
Q

What enzymes are involved in methylation of cytosine?

A

DNMT 1, 3a and 3b.

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10
Q

What class is DNMT1?

A

Maintenance, methylation pathways can be inherited when they divide.

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11
Q

What class are DNMT 3a and b?

A

Noval, add methylation to DNA which previously wasn’t.

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12
Q

What is SAM?

A

Universal methylation doner, acts as a co-factor.

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13
Q

What kinds of cytosines are methylated?

A

CPG dinucleotides.

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14
Q

What are CpG dinucleotide?

A

Cytosine that precedes a guanine.

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15
Q

Hoe many of the CpG sites in the genome are methylated?

A

70%

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16
Q

What are CpG islands?

A

Areas of the genome which have higher CpG sites.

17
Q

What is the importance of methylation in repetitive regions?

A

Keeps gene expression off.
Suppression of “invading” DNA.
Suppression of inappropriate transcription.

18
Q

What is the importance of methylation on the genome?

A

Transcription factors can’t bind so those genes are not expressed.

19
Q

How many CpGs are there within the genome?

A

Genome is very CpG poor.

20
Q

Where are CpG islands?

A

Within promotor regions.

21
Q

How many active X chromosomes do women have?

A

1

22
Q

How is the other X chromosome made inactive.

A

Methylation .

23
Q

Why is it important we have only 1 functioning X chromosome?

A

Because it prevents over expression of genes.

24
Q

What are imprinted genes?

A

Genes whose expression is determined by the parent that contributed to them.

25
Q

What is the function methylation mostly?

A

Attracts huge protein complexes which change histone position and represses gene expression because transcription factors cannot bind.

26
Q

Can methylation occur at different places?

A

Yes, CpA CpT CpC.

27
Q

What is hydroxy methylation?

A

The start of demethylation but not common as it can cause cancer.

28
Q

What kinds of histone modifications are there?

A

– Acetylation
– Methylation
– Phosphorylation
– Ubiquitination

29
Q

Where does the histone modification take place?

A

On their funky little tails.

30
Q

What happens when acetylation occurs on the histone?

A

Activation
Decompaction
DNA becomes permissive

31
Q

What happens when methylation occurs on the histone? K9 – H3 and K27 – H3

A

Inactivation
Compaction
Non-Permissive

32
Q

What is epigenetic drift?

A

The accuracy of which is DNA is methylated is much lower than DNA replication.

33
Q

What happens to DNA methylation with age?

A

DNA methylation pattern breaks down, reduction of CpG islands which leads to incorrect cell function.

34
Q

What is frailty?

A

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.

35
Q

What is the importance of methylation for frailty?

A

The more methylation you have the less frailty you have.

36
Q

Can methylation be used to predict age?

A

Clear correlation gives an indication of age based on methylation.
BUT only biological age.

37
Q

What can happen when you get abnormal methylation?

A

You become more prone to developing cancer.

38
Q

Why is DNA methylation important in regards to ageing?

A

If you prevent methylation you can sometimes prevent age-related diseases.

39
Q

What are HATs?

A

Histone acetyltransferase

Biology Of Ageing Year2 (23 decks)

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