chromatin

Question 1

what binds to the receptor to activate the signalling pathway to promote PKA

Answer 1

ligand

Question 2

what one type of cell can give rise to at least 220 different cell types

Answer 2

stem cells

Question 3

stem cells can give rise to how many different cell types

Answer 3

220

Question 4

what are the two different structures of DNA

Answer 4

euchromatin and heterochromatin

Question 5

what is the point in epigenetic regulation

Answer 5

to read genetic information in different manors enabling to generate the diff cells of our body

Question 6

embryonic stem cells can form how many different layers

Answer 6

3

Question 7

what are the 3 layers embryonic stem cells can form

Answer 7

mesoderm, ectoderm and endoderm

Question 8

what are the 4 different cell types

Answer 8

1. multipotent
2. primitive progenitor
3. lineage committed
4. specialised blood

Question 9

what do cells require before becoming specialised blood cells

Answer 9

further differentiation

Question 10

what do injuries, tissue damage, tissue regeneration, sun exposure and ischemia require in order to regenerate

Answer 10

the cellular processes have to occur simultaneously and therefore required coordination

Question 11

what enables stem cells and progenitor cells to re enter into proliferation and then differentiation

Answer 11

epigenetic regulations

Question 12

what do epigenetic regulations enable stem and progenitor cells to do

Answer 12

to re enter into proliferation and then differentiate

Question 13

what does epigenetic regulations enable stem cells and progenitor cells to differentiate into

Answer 13

regenerate tissue

Question 14

what is it called when epigenetic enables to read the genetic information in different manners

Answer 14

cell plasticity or genome reprogramming

Question 15

what is the human genome made out of

Answer 15

DNA

Question 16

where is DNA stored

Answer 16

the nucleus of eukaryotic cells

Question 17

how does a heterochromatin appear on a histogram compared to eurochromatin

Answer 17

darker

Question 18

heterochromatin contains what kind of DNA?

Answer 18

compacted (inactive)

Question 19

euchromatin contains what kind of DNA?

Answer 19

opened (active)

Question 20

why is euchromatin open?

Answer 20

so it can be read

Question 21

what structure do the euchromatin have

Answer 21

double stranded helical

Question 22

DNA is complexed with histones to form what

Answer 22

nucleosomes

Question 23

each nucleosome consists of how many histones?

Answer 23

8

Question 24

how many times does the DNA wrap around the 8 histones

Answer 24

1.65 times

Question 25

a chromatosome consists of what

Answer 25

a nucleosome plus the H1 histone

Question 26

the nucleosome folds up to produce what?

Answer 26

a 30nm fiber

Question 27

the 30nm fiber loops averaging what length?

Answer 27

300nm

Question 28

the 300nm fibers are compressed and folded to produce a fiber at what width?

Answer 28

250nm wide fiber

Question 29

tight coiling of the 250 nm fiber produces the chromatid of what

Answer 29

a chromosome

Question 30

why cant heterochromatin genes be read

Answer 30

they are closed

Question 31

what 8 histones form a nucleosome

Answer 31

2 H3, 2H4, 2 H2A and 2 H2B

Question 32

what level of DNA packing are nucleosomes

Answer 32

level 1

Question 33

what charge are AA's within nucleosomes

Answer 33

positive

Question 34

where do the nucleosomes bind tightly to?

Answer 34

negatively charged DNA

Question 35

what is an example of 2nd level packing

Answer 35

solenoids/chromatin

Question 36

in a solenoid, H1 histones aggregate causing what?

Answer 36

6 nucleosomes to coil together

Question 37

solenoids stack on top of each other forming what?

Answer 37

a chromatin fiber

Question 38

where do chromatin fibres attach themselves to

Answer 38

wall of the nuclear membrane

Question 39

when chromatin fibers are attached to the wall of the nuclear membrane what do they form

Answer 39

loops by binding to nuclear membrane proteins

Question 40

in the nucleus of a non dividing cell, chromatin fibers form what

Answer 40

discrete chromosome territories

Question 41

chromosome territories are correlated with what

Answer 41

gene densities

Question 42

territories of chromosome domains that are relatively gene rich tend to be located towards what

Answer 42

the interior of the nucleus

Question 43

the interaction of DNA/nucleosomes is regulated by what

Answer 43

histone modifying enzymes that induce post translational modifications

Question 44

name examples of histone modifying enzymes

Answer 44

1. histone acetyl transferase (HAT) 2. acetyl coA

Question 45

how are the histone modifying enzymes produced (HAT and acetyl coA)

Answer 45

glycolysis on lysine

Question 46

what does lysine do in order to regulate the strength of the binding of histone to DNA and opens genes to be expressed

Answer 46

it is a positive AA which binds strongly to negative DNA

Question 47

what does lysine do once it has bound to the negatively charged DNA

Answer 47

regulates the bindings of histones to the DNA and opens chromatins/genes to be expressed

Question 48

how are the expression of histone modifying genes and the activity of the histone modifying enzymes regulated

Answer 48

by cellular receptors and by energy metabolism

Question 49

acetylation/deacetylation of the positively charged amino acid lysine regulates what

Answer 49

interaction of negatively charged phosphate on DNA

Question 50

what processes regulate the interaction with negatively charged phosphate on DNA

Answer 50

acetylation/deactylation

Question 51

HAT enzymes catalyse the transfer of what to what

Answer 51

acetyl group from acetyl co A

Question 52

how is acetyl co A produced

Answer 52

in the TCA cycle

Question 53

where are the epsilon amino groups of lysine's located

Answer 53

in the N terminus of histones

Question 54

what does acetylation involve

Answer 54

abolishes the positive charge on lysine interacting with the negatively charged phosphate on the DNA backbone

Question 55

acetylation reduces what

Answer 55

the strength of the interaction histone/DNA

Question 56

interactions of DNA/nucleosomes is regulated by PTM but what is this induced by

Answer 56

cell signalling receptors and energy metabolism

Question 57

acteylation is an example of what process

Answer 57

PTM

Question 58

arginine an lysine can exist as what structures

Answer 58

mono, di, or tri-methylated

Question 59

what is methylation an example of

Answer 59

PTM

Question 60

what happens when a lysine is ubiquinated

Answer 60

increases the size of the lysine

Question 61

what is phosphorylation an example of

Answer 61

PTM

Question 62

phosphorylation can do what and why

Answer 62

repulses histones and DNA due to the several negative charges it places on the nucleotide (2)

Question 63

histones are modified where

Answer 63

on the C and N terminal domains

Question 64

what is the process that neutralises the positive charge of arginine

Answer 64

deamination or citrunillation

Question 65

what does deamination do to arginine

Answer 65

neutralises the positive charge, weakening the interaction with the negatively charged DNA, resulting in the opening of the chromatin

Question 66

methylation of lysine and arginine does what

Answer 66

regulates the hydrophobic interactions with histones

Question 67

histone modifying enzymes are expressed in what manner

Answer 67

tissue-dependant manner

Question 68

what do histone modifying enzymes do

Answer 68

open or close access to a gene

Question 69

for gene expression (transcription) to occur, the enzymes that synthesise RNA (RNA polymerase) must attach to what

Answer 69

a promotor region

Question 70

what enzymes synthesise RNA

Answer 70

RNA polymerase

Question 71

promotors contain specific DNA sequences called what

Answer 71

response elements

Question 72

how many different types of RNA polymerase are there

Answer 72

3

Question 73

the RNA polymerase auto assemble together to form what

Answer 73

RNA transcription machinery that binds and opens the double stranded DNA helix and then slide along the helix, this opens and closes the SNA whilst synthesising the new RNA molecule

Question 74

what are transcription factors

Answer 74

proteins that bind to specific DNA on a specific region to recruit the RNA polymerase to this specific location of the genome and initiate the transcription

Question 75

what 3 things can transcription factors bind to

Answer 75

enhancers, silencers and promoters

Question 76

what are enhancers

Answer 76

DNA sequences localised in non-coding regions (all but exons) to increase the chance that transcription of a particular gene will occur

Question 77

what are silencers

Answer 77

opposite of enhancers made of DNA and bind to transcription factors like enhancers but they inhibit or abolish the gene transcription