The Epigenome

Question 1

What is the nucleosome made up of?

Answer 1

Histone proteins and DNA

Question 2

What are the features of euchromatin?

Answer 2

Gene rich, Transcriptionally active, less wound up and unique DNA sequences

Question 3

What is another name for euchromatin?

Answer 3

Compartment A

Question 4

What are the features of heterochromatin?

Answer 4

Gene poor, less Transcriptionally active, condensed appearance and a repetitive DNA sequence

Question 5

What is another name for heterochromatin?

Answer 5

Compartment B

Question 6

What is a definition for the epigenome?

Answer 6

The sum of all (heritable) changes in the genome that doesn’t occur in the primary DNA sequences and that affect gene expression

Question 7

What does a change in the epigenome result in?

Answer 7

A change in the phenotype, not the genotype

Question 8

What are the mechanisms that regulate gene expression?

Answer 8

DNA methylation and histone modification

Question 9

What is DNA methylation?

Answer 9

Addition of a methyl group in the 5’ position of a cytosine

Question 10

What is DNA methylation?

Answer 10

Addition of a methyl group in the 5’ position of a cytosine

Question 11

What is DNA methylation catalysed by?

Answer 11

DNA methyltransferase enzymes

Question 12

Which DNA methyltransferase enzymes catalyse DNA methylation?

Answer 12

DNMT1, DNMT3a and DNMT3b

Question 13

What provides the methyl group for DNA methylation?

Answer 13

S-adenosyl methionine

Question 14

Where does DNA methylation occur in differentiated cells?

Answer 14

CpG dinucleotides

Question 15

What does DNA demethylation do?

Answer 15

Turns transcription off by preventing the binding of transcription factors

Question 16

What is histone modification?

Answer 16

Addition of chemical groups to the histone

Question 17

What are the four common modifications?

Answer 17

Methylation, acetylation, phosphorylation and ubiquitination

Question 18

How are the modifications named?

Answer 18

Based on the histone, amino acid and actual modification

Question 19

What are the three types of histone modifiers?

Answer 19

Writers, readers and erasers

Question 20

What are the two examples of writers?

Answer 20

Histone acetyltransferases and histone methyltransferases

Question 21

What are the writers?

Answer 21

Enzymes that add histone modifications

Question 22

What are the readers?

Answer 22

Proteins that bind to histone modifications and alter gene activity and protein production

Question 23

What are two examples of readers?

Answer 23

Bromodomain and extra-terminal proteins and chromodomain proteins

Question 24

What are erasers?

Answer 24

Enzymes that remove histone modifications

Question 25

Give some examples of erasers?

Answer 25

Histone deacetylase and histone demethylase

Question 26

What does histone acetylation at lysine residues do?

Answer 26

Relax the chromatin structure by reducing the positive charge on the histones, making it accessible for transcription factors

Question 27

What can histone methylation do?

Answer 27

Can repress or activate transcription depending on where it occurs

Question 28

What is X-inactivation?

Answer 28

Inactivation of one of the two chromosomes in every female somatic cell

Question 29

Why is X-inactivation necessary?

Answer 29

Needed as the Y chromosome has almost no genes

Question 30

What is the process of X-inactivation?

Answer 30

The X-ist gene is transcribed as long non coding RNA from the X-inactivation centre and binds all over the X-chromosome Histone acetylation is removed and histone and DNA methylation occurs Inactive X-chromosome is heterochromatic Tsix is derived by transcription in the opposite direction and antagonises Xist RNA to keep one X active

Question 31

Why are all tortoiseshell cats female?

Answer 31

Random X inactivation results in random patches of orange and black fur

Question 32

What is gene imprinting?

Answer 32

The selective expression of genes related to the parental origin of the gene copy

Question 33

What are imprinted genes mediated by?

Answer 33

Imprinting control regions

Question 34

What are essential to the genetic imprinting process?

Answer 34

Long noncoding RNAs

Question 35

When are imprinting patterns reset?

Answer 35

During gamete formation

Question 36

How is the non-imprinted gene inactivated?

Answer 36

DNA methylation and histone methylation

Question 37

What is pharmacoepigenetics split into?

Answer 37

Epigenetic regulation of genes and epigenetic effects of drugs

Question 38

What does the changing the Epigenetic regulation of genes do?

Answer 38

Increasing the efficacy of drugs

Question 39

What does changing the epigenetic effects of drugs do?

Answer 39

New paradigms for drug treatment

Question 40

What are the epigenetic enzymes that are normally mutated in tumour cells?

Answer 40

``` DNMT3A and TET1/2 Histone acetyltransferases Histone methyltransferases Histone kinases Histone readers Histone demethylases ```

Question 41

Give some examples of pharmacoepigenetic drugs

Answer 41

DNA methyltransferase inhibitors and histone deacetylase inhibitors