Regulation of Eukaryotic Chromosomes

Question 1

what are the two histone variants of h3

Answer 1

h3.3 and cenpa/ cenh3

Question 2

what are the four core histones

Answer 2

h3, h2a, h4 and h2b

Question 3

centromeres are characterised by a centromere specific histone h3 variant called

Answer 3

cenpa or cenh3

Question 4

centromeres often have heterochromatin that is rich in what

Answer 4

satellite DNA sequences

Question 5

what is chromatin remodeling

Answer 5

the energy dependent displacement or reorganisation of nucleosomes that occurs in conjunction with activation of genes for transcription

Question 6

remodeling complexes can do what to nucleosomes

Answer 6

alter, slide or displace nucleosomes

Question 7

there are numerous ___ dependent chromatin remodeling complexes

Answer 7

ATP

Question 8

list three histone post translational modifications

Answer 8

lysine methylation, lysine acetylation, lysine ubiquitilation

Question 9

histone tails are highly

Answer 9

conserved

Question 10

what is a direct effect of modifying amino acid side chains on histone tails

Answer 10

a change in charge

Question 11

what is an indirect effect of modifying amino acid side chains on histone tails

Answer 11

recruitment

Question 12

methylation of lysines is done by

Answer 12

histone methyltransferases

Question 13

demethylation of lysines is done by

Answer 13

histone demethyltransferases

Question 14

acetylation of lysines is done by

Answer 14

histone acetyltransferases

Question 15

deacetylation of lysines is done by

Answer 15

histone deacetylase

Question 16

acetylation of lysine residues in histone tails results in

Answer 16

a loss of positive charge to neutral charge

Question 17

when lysine is acetylated, the loss of positive charge results in

Answer 17

a reduction in binding to DNA, opening up of chromatin and access to DNA

Question 18

histone modification enzymes are targeted to specific genomic regions how?

Answer 18

through transcription activators

Question 19

lysines being acetylated causes transcriptional

Answer 19

activation

Question 20

methylation of lysine residues is context dependent, they can recruit

Answer 20

activators or repressors of transcription

Question 21

methylation of lysine 9 on histone h3 results in

Answer 21

heterochromatin assembly and transcriptional silencing

Question 22

what recognises methylated lysines

Answer 22

chromodomains

Question 23

what recognises acetylated lysines?

Answer 23

bromodomains

Question 24

what is the fifth base?

Answer 24

5-methylcytosine

Question 25

what catalyses the reaction of the addition of a methyl group to cytosine

Answer 25

DNA methyltransferases

Question 26

roughly how many CpGs in human somatic cells are methylated

Answer 26

70-80% referred to as global methylated

Question 27

where do the greatest amount of CpG methylations occur

Answer 27

in satellite DNA, repetitive elemtns,

Question 28

in some areas CpGs are unmethylated what are these called

Answer 28

CpG islands

Question 29

about how many CpG islands exist in the human genome

Answer 29

45,000

Question 30

where are unmethylated CpG islands located

Answer 30

in the promoters, first exons of 50-60% of human genes

Question 31

CpG islands are present in nearly all

Answer 31

active housekeeping genese

Question 32

what does DNA methylation do?

Answer 32

it compacts chromatin and is associated with transcriptional repression