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Cell Molec > Lecture 20 > Flashcards

Lecture 20 Flashcards

1
Q

What phase of the cycle is where the cell grows in size?

A

G1

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2
Q

What phase of the cell cycle arrests cells that do not actively go through the cell cycle?

A

G0

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3
Q

What phase of the cell cycle where DNA is replicated?

A

S phase

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4
Q

What phase ensures and checks that the cell is ready to undergo cellular division?

A

G2

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5
Q

What are cyclin-dependent kinases (CDKs)

A

cell-cycle stage-specific small protein kinases that require a regulatory cyclin subunit for their activity

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6
Q

Function of CDKs between after the end of G1 and before the start of S-phase?

A

duplicate centrosomes

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7
Q

What will M-phase specific CDKs trigger?

A

the actual splitting of centrosomes to opposite poles of the cell = becomes spindle poles

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8
Q

What are the phases in interphase?

A

G1, S, G2

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9
Q

Which phase do microtubules attach to the chromosomes?

A

prometaphase

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10
Q

After DNA replication, what are the two sister chromatids held together by?

A

cohesins

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11
Q

What are cohesins?

A

protein complexes

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12
Q

What is a centromere?

A

a DNA sequence in the center of the chromosomes

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13
Q

What is a kinetochore?

A

a protein complex that binds to the centromere and to the (+) ends of the kinetochore specific microtubules as well

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14
Q

What are the three major classes/types of microtubules in cell division?

A

kinetochore MTs, astral MTs, and polar MTs

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15
Q

What are astral MTs? What do they attach to

A

radiate behind the spindle poles and anchor onto plasma membrane maintaining the separation of poles

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16
Q

What are polar MTs?

A

MTs that come to the middle of the cell but do not attach to a chromosome, their distal ends will overlap the other polar MTs from the other spindle pole

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17
Q

What phase in mitosis are chromosomes captured and oriented?

A

prometaphase

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18
Q

What occurs once kinetochore MTs attaches to the kinetochores on the chromosome?

A

orientation begins

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19
Q

What is congression?

A

the assembly/disassembly of MTs from each spindle pole to get the chromosome oriented correctly = back and forth pull

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20
Q

What happens if congression isn’t correctly done?

A

can lead to translocation due to one of the MTs not correctly attached to chromosome

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21
Q

Which motor proteins specifically help with congression?

A

Kinesin-13 and dynein

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22
Q

How does the MTs move?

A

via assembly/disassembly of the tubulin protofilaments

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23
Q

What does it mean to “capture” the chromosome?

A

to get it in the direct middle of the dividing cell

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24
Q

What is the chromosomal passenger complex?

A

basically part of the kinetochore complex, proteins that fit over the MTs in a sleeve-like manner

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25
Q

Function of chromosomal passenger complex?

A

regulates MT attachment at kinetochores

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26
Q

What special kinase is involved with the chromosomal passenger complex?

A

aurora B kinase

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27
Q

what is the function of aurora B kinase?

A

phosphorylates chromosomal passenger complex to inhibit tight MT attachment

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28
Q

Why would you want aurora B kinase to inhibit strong MT attachment to your chromosomes?

A

in the cases prior to prometaphase, ensure that the chromosomes are oriented and captured properly before MTs tightly bind to them

29
Q

When does aurora B phosphorylate?

A

when the chromosome is not under tension and the aurora B’s are close to phosphorylate each other

30
Q

What causes the tension in the chromosomes?

A

congression

31
Q

How does Anaphase A move chromosomes to poles?

A

via MT shortening

32
Q

what ends can kinesin-13 disassemble from?

A

from (+) or (-) ends

33
Q

What do polar MTs do to help in Anaphase?

A

separate/push spindle poles away from each other via kinesin 5 (sliding kinesin)

34
Q

How are astral MTs anchored?

A

via dynein (goes towards (-) end) = toward the spindle poles (MTOC)

35
Q

What are the two parts of Anaphase?

A

A and B

36
Q

What happens in Anaphase A?

A

chromatids are actually separating

37
Q

What happens in Anaphase B?

A

the cell is pushing the spindle poles in opposite directions to make sure everything is separated from each other

38
Q

What type of kinases is CDKs?

A

Serine and threonine, NOT Tyrosine

39
Q

How are CDKs regulated?

A

by phosphorylation or dephosphorylation or degradation via ubiquitin

40
Q

When are cells irreversibly committed to cell cycle?

A

at the restriction point/START

41
Q

What phase marks the commitment of cells to the cell cycle?

A

S-phase because you don’t want double sets of DNA in one cell

42
Q

Which transcription factor is associated with metazoans (our) restriction point?

A

E2F

43
Q

How can E2F be inactivated?

A

when Rb (retinoblastoma) is bound to it

44
Q

What cyclins are involved with entry into the cell cycle?

A

Cyclin E or A

45
Q

What activates cyclin D with associated CDKs?

A

growth factors - messages from other cells

46
Q

What is the function of cyclin D CDKs?

A

phosphorylates Rb to remove it from E2F to initiate transcription

47
Q

Function of E2F

A

transcription factor that can initiate the transcription of cyclin A or E

48
Q

What represents the restriction point?

A

cyclin A/E CDK

49
Q

One of the functions of cyclin E/A with CDK?

A

keeps Rb phosphorylated

50
Q

At what phase will the centrosomes separate from each other?

A

Mitosis

51
Q

What CDK triggers the duplication of chromosomes?

A

CDK2

52
Q

When does centrosome duplication start and end?

A

right after G1 and just at the end of G2 (goes thru S-phase)

53
Q

When is the APC/C (anaphase promoting complex) active?

A

At 2 different points in the cycle: activated to promote anaphase and within anaphase, and at the exit of M-phase

54
Q

What is the anaphase-promoting complex? (APC/C)

A

it is a ubiquitin ligase

55
Q

What is the function of APC/C?

A

to degrade S-phase and mitotic CDKs after their phases are over

56
Q

What is the purpose of Cdh1?

A

to activate APC/C

57
Q

What is the S-phase cyclin-CDK complexed within G1?

A

Sic1

58
Q

What is Sic 1?

A

a protein that prevents DNA replication until everything in G1 has been completed and the restriction point has been passed, acts like a checkpoint in a way

59
Q

How can the cell cycle be regulated where we don’t go backward or jump phases?

A

via phosphorylation/dephosphorylation and proteasomal degradation of CDKs

60
Q

At what phase is DNA replication prepared?

A

G1

61
Q

In G1, how does the cell cycle prepare for DNA synthesis?

A

origin-recognizing complex binds to the origin of replication and helicases bind to the complex = everything is loaded but nothing is active

62
Q

What activates DNA replication in S-phase?

A

S-phase CDKs via phosphorylation

63
Q

How do cohesins work?

A

accessory proteins load cohesins onto the unreplicated strand so that the replicated strand will go through within the cohesins

64
Q

What associates at the centromere post S-phase (G2 phase)

A

protein phosphatases

65
Q

What is the function of protein phosphatases for chromosomes during G2?

A

protein phosphatases will protect cohesin-centromere pair from becoming phosphorylated so that it does not fall off like the rest of those on the chromosome

66
Q

Why are protein phosphatases necessary in G2?

A

G2 is before mitosis = need to keep sister chromatids together before mitosis starts

67
Q

When does the nuclear envelope breakdown?

A

prometaphase

68
Q

What happens in telophase

A

contractile ring assembly, nuclear envelope reassembly

Cell Molec (16 decks)

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