DNA modifications/RNA polymerase II/ Transcription

Question 1

Chromatin structure is controlled through (2)

Answer 1

1. Histone Modifications

2. DNA Methylation

Question 2

Types of histone modifications (3)

Answer 2

1. Phosphorylation
2. Methylation
3. Acetylation

Question 3

Modifications to histones determine

Answer 3

how tightly the DNA is coiled.

Methylation closes DNA
Acetylation opens DNA

Question 4

Histone acetylation leads to

Answer 4

uncoiling of chromatin

Question 5

When chromatin modifications are inherited it is called

Answer 5

epigenetics

Question 6

DNA is usually methylated at

Answer 6

cytosine residues next to guanine

‘Cpg islands’

Question 7

DNA methylation usually

Answer 7

silences a gene

‘turns off’

Question 8

DNA methylation enzyme

Answer 8

Methyl transferase

Question 9

DNA methylation silences genes in two ways:

Answer 9

1. Physically hinder
   the binding of TFs
2. Transcriptionally silence with MBDs
   methyl Cpg binding domain proteins: recruit proteins to modify the histones to form dense heterochromatin (inactive)

Question 10

Different chromosomes occupy different

Answer 10

‘territories’ in the nucleus

influences gene expression through co localisation of nuclear machinery

Question 11

RNA polymerase II structure (5)

Answer 11

• has 12 subunits
• has a CTD which carries splicing machinery
• contains transcription factors
• cannot correct mistakes
• contains Mg2+ or Mn2+

Question 12

Transcription is regulated by transcription factors that bind to

Answer 12

promotor or enhancer sequences

Question 13

Core promotor sequences (5)

Answer 13

• GC box
• CAAT box
• BRE box
• TATA box
• Initiator

Question 14

RNA polymerase II contains

Answer 14

transcription factors TFIIB, D,E,F,H

which bind to promotor sequences or initiate transcription

Question 15

TFIID binds to the

Answer 15

TATA box

initiates recruitment of other factors and regulates binding of TBP (tata binding protein TF)

Question 16

TFIIB binds to the

Answer 16

BRE box

positions RNA pol II at initiator site

Question 17

TFIIF stabilises

Answer 17

interaction between TBP (tata binding protein, a TF) and TFIIB

Question 18

TFIIE attracts

Answer 18

TFIIH

Question 19

Mutations in the TFII complex cause (2)

Answer 19

- DNA repair disorders
Xeroderma pigmentosum (skin cancers)

• Premature ageing syndromes
  Cockayne’s syndrome

Question 20

DNA enhancers recruit

Answer 20

• other proteins that cause DNA looping
• bring mediator proteins into contact with transcription machinery
• are distant from gene (to make loop)
• function in either direction

Question 21

DNA insulators are a segment of DNA that acts as

Answer 21

a boundary between 2 genes

can silence a gene

• regulate enhancers
• regulate multiple genes
• can act as chromatin boundary markers