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Flashcards in Mitosis Deck (26):
0

Functions of mitosis

Replicate DNA accurately, segregate chromosomes, replicate cell structures, divide cells

1

Cell phases

G1 - growth, longest phase by far
S - synthesis, replication of chromosomes and centrioles
G2 - growth, duplication of organelles, proteins for mitosis
M - mitosis, very short

2

Karyokinesis

Division of nucleus

3

Cytokinesis

Division of cytoplasm and cell contents

4

Interphase

Includes G1, S, G2
G0 if cell has left cycle

5

Duplication of centrioles

Pair splits, each becomes nidus for new centriole
Reform gamma tubulin and capping proteins
MTs nucleate through gamma tubulin rings

6

Deviations from cell cycle

G0 - quiescent phase (not good environment)
Gtd - terminal differentiation (muscles, nerves)

7

Prophase

Chromatin condenses to chromosomes, nucleolus breaks down
Centrioles migrate, MTs develop

Late prophase - nuclear envelope breaks down

8

Chromosome condensation

Condensin increases coiling
Cohesin binds sister chromosomes

9

Dissolution of nuclear envelope

Occurs during "prometaphase"
M-CDK phosphorylates lamin
Breaks into small vesicles of lamin + membrane
Allows fast reassembly after mitosis complete

10

Microtubules during mitosis

Astral
Polar (connect MT to MT in spindle, push against each other to separate centrosomes)
Kinetochore (pull chromosomes towards centrosome)

11

Metaphase

Chromosomes migrate and align at equator of spindle via MT "tug of war"
MT's attach to kinetochores

12

Centromere

Region where sister chromosomes attach (DNA)
Kinetochore is complex of 30+ proteins that attach centromere to microtubules (plate structure)

13

Separation of chromatids

Anaphase promoting complex (APC) is phosphorylated when aligned
Ubiquitinates securin which is inhibitor of a cohesin protease
Securin destroyed ->protease active -> cleaves cohesin

14

Anaphase

A - chromosomes to centrosome via depolymerization of kinetochore MTs and dyneins on astral
B - poles apart via kinesins on polar MTs

15

Telophase

MT's depolymerize
Lamin, pore complexes dephosphorylated - nuclear membrane reforms
Chromosomes decondense
Actin contractile ring -> cytokinesis

16

Time of mitosis

Very short! 2-3 hours total

G1 determines whether rate of cell division
Cells that get to G2 will go through mitosis

17

Telomeres

Repeating sequences
Not always transcribed -> aging
Telomerase rebuilds and can extend lifespan

18

Regulation of cell cycle

Cyclins only present for short time, activate CDKs
CDKs always present, but must bind to cyclin to be active
Also regulated by phosphorylation (checkpoints)
Many targets (transcription factors, kinases, activate other cyclins)

Conserved across species
Can cause cancer...

19

S cyclin

Initiates DNA replication (S phase)

Joins with s-CDK
Phosphorylates pre-replicative complex which normally inhibits
Allows origin of replication complex (ORC) to begin fx

20

Cyclins

Only present for short period - translated, then ubiquitinated
Carry out function via CDK

21

Checkpoints

Regulate cyclins and CDKs based on "quality control"
G1 - env't favorable?
S - DNA damage?
G2 - DNA replicated?
M - sister chromosomes at equator?

22

Retinoblastoma

Inhibits transcription of proliferative proteins (via inhibition of transcription regulators) based on env't
G1/S cdk inactivates by phosphorylation, allowing replication to begin

Defects cause proliferation despite env't (cancer)

23

p53 mechanism

Always translated and broken down in cell

p53 is phosphorylated and stabilized if cell stress or DNA damage
Transcription upregulator of p21, which binds and inhibits G1/S-cdk
Also can initiate apoptosis

Most common cancer mutation (most cells)

24

Apoptosis

Programmed cell death, not inflammatory
Normal part of development, degraded or damaged cells
Triggered by p53, TNF, cytochrome c in cytoplasm (vs mitochondria), lack of growth factors, bad env't
Mediated by caspases
Nucleus and cell contents into vesicles -> phagocytosed

25

BCL2

"B cell lymphoma" 2 gene
Blocks apoptosis
Upregulated in melanoma, breast, prostate, lung, etc