Chromosomes and Genomes

Question 1

Characteristics of Heterochromatin

Answer 1

Compacted
Repressed or N/A gene expression activity
Higher histone density
Located at telomeres, centromeres, other repetitive regions
Replicates later

Question 2

Characteristics of Euchromatin

Answer 2

uncoiled 
active in gene expression activity 
lower in histone density 
located at protein coding DNA regions
Replicates earlier

Question 3

How is DNA protein complex held together?

Answer 3

By attraction between positively- charged amino acids (Arg, Lys) + negatively- charged sugar -PO4 backbone

Question 4

What are the histone tail modifications?

Answer 4

Lysine- acetylated and methylated
Arginine- methylated
Serines- phosphorylated

Question 5

writers are what?

Answer 5

proteins that ADD histone marks

Question 6

erasers are what?

Answer 6

proteins that REMOVE histone marks

Question 7

What is the writer and eraser for acetyl

Answer 7

HAT (acetyltransferase)

HDAC (deacetylase)

Question 8

What is the writer and eraser for methyl

Answer 8

HMT (methyltransferase)

HDM (demethylase)

Question 9

What is the writer and eraser for phosphate

Answer 9

kinase

phosphatase

Question 10

What is the writer and eraser for ubiquitin

Answer 10

Ubiquitin ligase U3

DUB (Deubiquiting enzyme)

Question 11

readers are what?

Answer 11

proteins that recognize histone marks

Question 12

What does acetylation do?

Answer 12

it activates (promotes euchromatin) by destabilizing histone-DNA interactions

Question 13

What does methylation do?

Answer 13

H3K4me3-activates transcription
H3K27me3- allows expression sometimes (facultative)
H3K9me3- never allows expression (constitutive)

Question 14

What does phosphorylation and Ubiquitination do?

Answer 14

recognized by proteins that remodel histones, to either increase or decrease histone density on DNA

Question 15

What is tethering

Answer 15

Creates a physical roadblock for the heterochromatin formation

Question 16

what is sheltering

Answer 16

physically shelters euchromatin from view of the wave

Question 17

what is re writing

Answer 17

marks reverse the tide

Question 18

What is epigenetic

Answer 18

heritable changes in gene expression without the corresponding alteration of the DNA sequence

Question 19

True or false: are histone marks heritable?

Answer 19

True

Question 20

True or false: can DNA be methylated and or acetylated like histones?

Answer 20

True

Question 21

What diseases can changes in DNA methylation result in?

Answer 21

Imprinting disorders: increased risk to IVF babies and or related to developmental genes
cancer: hypermethylation turns off tumor suppressor genes and hypomethylation destabilizes chromosomes