Chapter 2: Structure Of Chromatin

Question 1

The charge of DNA

Answer 1

Negatively

Question 2

Charge of histones

Answer 2

Positive

Question 3

Which amino acid in high proportion makes the histone positive?

Answer 3

Lysine and Arginine

Question 4

What is a Nucleosome

Answer 4

When a 200bp DNA wraps around a histone octomer[2 molecules of 4 core histones namely: H2A H2B H3 H4]
》146bp wraps around October
》remaining servers as a link to other October

Question 5

Nucleosome structure n position can be altered by

Answer 5

Chromatic remodeling 
(Chromatic remodeling complex-crc)

Question 6

Are complexes of proteins that bring about a change in chromatic compaction

Can act as activating or repressing complex

They disrupt DNA-histone interaction

Answer 6

Chromatic remodeling complex

Question 7

Effect of chromatin on nucleosome

Answer 7

》when the cumbersome structure changes 》 DNA is more exposed
》nucleosome is displaced》 moves to another position
》nucleosome is lost

Question 8

Crc can exchange subunits within the nucleosome how?

Answer 8

By replacing the nucleosome

Question 9

Histone modification (HMs) examples

Answer 9

P -- PHOSPHORYLATION 
U -- UBIQUITINATION
M -- METHYLATION 
A -- ACETYLATION
S -- SUMOylation

Question 10

What is ACETYLATION and it’s effect

And it’s catalyzed by what

Answer 10

》+ Acetyl group to lysine tail of histones
》Catalysed by Histone acetyl-transferase( HAT)
》ACETYLATION decrease nett +charge of histones 》more open structure
》 associated with gene activation

Question 11

HDAC abbreviation

Answer 11

Histone deacetylase

Question 12

METHYLATION

Answer 12

》+ of methyl group to lysine at N terminal tail
》catalyzed by histone methylase(HMT)
》does not reduce + chsrge of aa

Question 13

Effects of METHYLATION on chromatin structure

Answer 13

》modification on H3 lysine 4 promotes gene activation

》modification on H3 Lysine 9&27 repress gene activation

Question 14

UBIQUITINATION

Answer 14

》is a small protein of 76aa
》 links onto 2 H2A or H2B
》decrease the +charge of Histones
》can recruit HMT- histone methylase

Question 15

SUMOLYTION

Answer 15

》leads to recruitment of HDAC(HISTONE DEACETYLASE

》it will repress transcription

Question 16

PHOSPHORYLATION

Answer 16

》 is negatively charged 》 thus will neutralize + charge of histones

Question 17

Loose nucleosome fold and condense from ..nm to …nm

Answer 17

10nm to 30nm

Question 18

Example of how HM can cause transition from 30nm to 10nm

Answer 18

》The + charge of tail of H4 interact with - region of H2A 》promotes close packaging

》acetylation at H4 promotes open chromatin structure

Question 19

H1 & histone varients Play a role in 10nm to 30nm transition how

Answer 19

H1 recruits a DNA methylase enzyme 》 this inhibits recruitment of HMT》 WHICH RESULTS IN PACKAGED PACKED STRUCTURE

Histone varient 3.3 inhibits recruitment of H1》 leads to open structure

Question 20

LCR

Answer 20

Locus control region

Question 21

What are LCRs

Answer 21

》DNA elements that regulate chromatin structure
》responsible for activation of genes under its control
》causes more expression of the genes》 leads to open confirmation
》 perform its function over long distance

Question 22

Insulators

Answer 22

》BLOCKS THE EFFECTS OF LCRs

Question 23

The CtCF protein binds to insulators and they interact with themselves to form a loop/strand?

Answer 23

Loop