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P&R > Cell cycle > Flashcards

Cell cycle Flashcards

1
Q

Three major checkpoints

A

G1-to-S transition
G2 checkpoint
DNA damage checkpoint

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2
Q

G0 phase associated with

A

quiescence

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3
Q

Gap phase decision

A

Divide again, or not

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4
Q

What do mammalian cells monitor during G1 phase?

A

Extracellular signals (AKA growth factors or mitogens) or tissue integrity (contact with neighboring cells)

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5
Q

What is happening during S phase?

A

Make a copy of each chromosome

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6
Q

What do cells monitor during interphase

A

DNA damage

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7
Q

T/F. G2 length is fixed

A

False, G2 length is variable

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8
Q

What do cells monitor during G2 phase

A

Completion of DNA replication, size and DNA integrity

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9
Q

What happens when problems are detected by proteins that activate G2 checkpoint?

A

G2 is prolonged by blocking entry into M-phase, giving cells time to fix the problem

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10
Q

What is monitored by the spindle checkpoint

A

chromosome capture

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11
Q

how is spindle checkpoint activated?

A

by signaling from uncaptured kinetochores

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12
Q

what is the most rapid stage of the cell cycle

A

mitosis

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13
Q

what does the MTOC do?

A

microtubule organizing center - it duplicates and builds mitotic spindle

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14
Q

what physical changes happen during mitosis (6)

A
  1. MTOC duplicates and builds spindle
  2. Chromosomes condense into tight structures
  3. Nucleus disassembles
  4. Spindle microtubules capture and separate sister chromosomes (AKA segregation)
  5. Cell pinches in half (AKA cytokinesis)
  6. Chromosomes coalescene and nucleus reassembles
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15
Q

prophase accomplishments

A

centrosomes separate

chromosomes condense

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16
Q

prometaphase accomplishments

A

nuclear envelope breaks down

chromosomes attach to spindle

17
Q

metaphase accomplishments

A

chromosomes align on spindle equator

18
Q

anaphase accomplishments

A

sister chromatids separate and move to poles
cleavage furrow assembles
organized central spindle assembles
poles separate

19
Q

telophase accomplishments

A

cleavage furrow constricts

nuclear envelope assembles

20
Q

cytokinesis accomplishments

A

chromosomes decondense
interphase microtubule network reforms
daughter cells separate

21
Q

how do proteins drive cell cycle forward?

A

by the activity of protein kinases (Cdks)

22
Q

what do cdk proteins require for their activity

A

cyclin proteins

23
Q

what are cyclins destroyed by

A

proteolysis

24
Q

cyclin destruction is triggered by

A

activated Cdk-complex

25
Q

why does CDK phosphorylation matter?

A

it phosphorylated specific sets of target proteins that changes their activity - for example lamins, which leads to nuclear disassembly

26
Q

what modification does full activity of Cdk-cyclin require?

A

phosphorylation at activating site

27
Q

what regulates phosphorylation at Cdk-cyclin activating site

A

Wee1 kinase (inactivates with inhibitory phosphate) and Cdc25 (phosphatase)

28
Q

how do CKIs work

A

They bind to cyclin-CDK and physically block active phosphorylated site, inhibiting activity

29
Q

how do ubiquitin ligase complexes affect cell cycle?

A

APC and SCF drive cell cycle by tagging cyclins and other proteins for proteolysis

30
Q

APC activity

A

promotes exit from mitosis by poly-ubiquitinating M-phase cyclins and chromosome glue

31
Q

T/F. SCF complex is constitutively active

A

True

32
Q

How does SCF work?

A

Promotes EXIT from G1 and entry into S-phase by degrading p27, and later degrades G1/S cyclins to push into S-phase

33
Q

what must cells do to pass restriction point?

A

inactivate retinoblastoma, Rb binds/inhibits E2F, a TF that turns on S-phase genes

34
Q

what triggers G1/S transition ?

A

inactivation of Rb and activation of S-phase CDK

35
Q

how does p53 work?

A

it’s a TF, activates genes that arrest cell cycle, allowing time for DNA repair. If repair efforts fail, p53 triggers apoptosis

36
Q

what activates G2/M checkpoint

A

DNA damage

P&R (15 decks)

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