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Genes and gene expression > DNA replication and cell cycle > Flashcards

DNA replication and cell cycle Flashcards

1
Q

cell cycle phases

A

g1
g2
m
s

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2
Q

S phase processes

A

Unfold chromatin structure
copy DNA completely and accurately
Refold DNA back into chromatin

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3
Q

DNA replication elongation

A

how the replication fork moves through a region of DNA
is in semi discontinuous fashion
leading and lagging strands

bi directional

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4
Q

Proteins active at replication fork

A

helixcase to open dna strand
polymerase / pcna and rpa for leading strand

polymerase
primase
pcna
dna ligase
etc for lagging strand

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5
Q

Helicase

A

unwinds the dna strand
made up of 6 proteins called mcm
complexed with cdc45 and GINS complex - CMG
Specific regions of genome may have their own helicases

ws for ribosomal repeates

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6
Q

Leading strand factors

A

polymerase - synthesises DNA
Rpa- single stranded binding protein - protects it
Pcna - processivity factor for the polymerase - keeps polymerase associated to dna

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7
Q

Lagging strand factors

A

Okasaki fragment initiation by DNA polymerase alpha
Primase - synthesis of RNA primer
Polymerase- DNA synthesis

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8
Q

lagging strand factors 2

A

polymerase alpha starts of process then polymerase switching occurs.

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9
Q

lagging strand factors 3

A

joining of okasaki fragments by rnaseh, fen1 and dna2
rfc,pcna,polymerase
and with DNA ligase it all becomes connected

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10
Q

Initation of replication

A

DNA component- origin of replication
protein components - the machinery of initiation

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11
Q

origin of replication

A

ARS - autonomously replicating sequences

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12
Q

Initation proteins

A

ORC - origin recognition complex
Cdc6
Cdt1
MCM complex

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13
Q

The initation pathway

A

ORC binds to DNA
recruites CDT1 and CDC6
CDT1 loads MCM proteins onto chromatin - preRC complexs formed

other proteins then joined and pre initiation complex formed
then elongation

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14
Q

Termination

A

replication forks stop when they hit each other.

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15
Q

Replication fork barriers

A

Termination sites where forks stop

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16
Q

general points

A

all origins do not fire at same time
genome is divided into early and late replicatin regions

early - euchromatin

late - silent and heterochromatin

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17
Q

Replication occurs in replication factories

A

enzymes are held onto frame works
points of replication seem to be cluseted into 300 sites - multiple forks at each site called rep factories

18
Q

Linear chromosomes habe specialised end

A

causes shortening of chromosomes
telomeres are at end
replicated by telomerase that add extra repeates at end

19
Q

mechanics of mitosis

A

prophase - chromosome condensation
metaphase - chromosome congression
anaphase ab- sisterchromatid seperation and cleavage furrow formation

telophase - dna seperates into two different nuclei

20
Q

chromosome condensation

A

dna is compressed to make it shorter and fatter.
main protein in this is condensin - structure two globular hand and hinge to attach to dna and flex.
condensin may form rings around chromatin
either by random or similar to cohesin action

21
Q

metaphase structures

A

kinetochore
spindle
spindle pole bodies

22
Q

the kinetochore

A

region on chromosome attached to spindle
complex structure - multiple regions
DNA - centromeric heterochromatin - very repetitive

proteins - many types, structural, sequence specific and molecular motors

23
Q

the spindle and spindle pole bodies

A

pole bodies - two tubues of tubulin at right angles to each other surrouned by pericentriole material where microtubules are ennucleated

spindle - microtubulin made of a and b tublin and has plus/minus end. has directionality

24
Q

spindle dynamic

A

spindle pole duplicates to give two.
new ones moive to edge assisted by motors
spindle generated
invades region of chromosomes and looks for kentichore.
microtubules sento to cytoplasm to anchor

25
Q

Anaphase

A

chromosome pulled toward poles by molecular motors and microtubule shortening
a- toward poles
b- poles move apart

26
Q

telophase

A

two new nuclei form and the chromosomes decondense
next cytokinesis

27
Q

systems help in understand mitosis

A

biochem and genetics in yeast - condensation and kinetochore structure

spindle stuff - biochem on xenopus invitro extracts

28
Q

control of cell cycle

A

phosphorylation
and cdks

29
Q

identification of cdks

A

yeast cell division mutants
xenopus oocytes and eggs

30
Q

cdk kinases

A

2 sub units
kinase subunit
cyclin subunit-controller and determines specificity

31
Q

cyclin cdk complexes

A

redundacies in cyclin so we can llose some types and still allows for cell sruvival

32
Q

what do cdks do

A

phosphorylate key groups of proteins - changes activity state of proteins and drives cell into next phase of cell cycle

e.g. replication initation protein

some proteins repressed or activated
cdks can have diff effects on same proteins

modiifcation not permenant cdk needed to be present to sustain

33
Q

cell cycle characterised ?

A

by cyclin activity
one cdk can modify next cdk to be active / next cdk can decrease the cdk before it

34
Q

how is cyclin cdk activity is controlled ?

A

by transcription , proteolysis - act on clclin not cdk

modification, inhibition, cell localisation - act on cdk/cyclin complex

35
Q

cyclin transcriptional control

A

growth factors - activate transcription factors - activation of cyclin genes or activation of other cell cycle controlled proteins

36
Q

proteolysis of cyclin

A

negative effect
at g2 to m phase transition cyclin b is broken down by first being modified by ubiquitin chain then proteosome breaks it down

37
Q

modification of cdk/cyclins

A

positive or negative

negative - wee1 kinase for cdc2 inactivation
positive - cdc25 phosphotase - activates cdc2

38
Q

cdk inhibitors

A

sic, rum sp

p21 - cdk 1/2
p28 - cdk 1/2/4/5

39
Q

variation to basic cycle 1

A

meiosis
2 rounds of nucler division

40
Q

polymitosis

A

cell carries out multiple rounds of mitosis with no intervening dna replication
happens in polyploid tissue

41
Q

polyploidisation

A

mutliple rounds of replication with no intervening mitosis
form clumps of dna or polytenisation

42
Q

amplification

A

multiple initations
causes a nested structure
extra dna added to dna through recombination

Genes and gene expression (8 decks)

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