Lecture 12 Flashcards
The cell cycle is driven by
cyclin dependen kinases (Cdks)
Cdks _____ key proteins to control their function
phosphorylate
Cohesin rings are added when _________ and hold _____ together until _______
DNA is replicated
sister chromatids
anaphase
The centrosome must duplicate in what phase?
S phase
The centrosome nucleates more MTs in what
mitosis
Each daughter cell gets a ______after _____
centrosome
cytokinesis
The spindle contains how many dif groups of microtubules?
3
what three microtubules do the spindles contain?
astral MT
kinetochore MT
interpolar MT
Kinetochore MTs
MTs have to find and attach to the kinetochores - must be able to undergo co-ordinate assembly and disassembly
interpolar MTs
MTs growing from one pole must meet those from the other pole and form anti-parallel interactions
Astral MTs
highly dynamic
crucial role in anaphase
The number of microtubules nucleated by the centrosomes ______ from prophase
increases
Catastrophe
when MTs switch from growing to shrinking
Why do dynamics increase? (and what is the result)
- some MAPs are inactivated when phsphorylated by the mitotic kinase M-Cdk
- proteins that trigger microtubule catastrophe are activated in mitosis
result: more chance of MTs growing from each centrosome contacting each other or chromosomes
What does the activation of condensin do?
chromosomes condense (prophase)
What does the activation of microtubule catastrophe proteins do?
microtubules more dynamic
What does the inactivation of MAPs do?
microtubules more dynamic
what does the inactivation of nuclear lamins do?
nuclear envelope disassembles
What happens in prophase
chromosomes condense in prophase because condensins compact the DNA
What are condensins activated by in prophase?
by phosphorylation by M-Cdk
What happens when the bipolar miotic spindle starts to form?
MTs growing from the two centrosomes meet and start to interact via antiparallel interactions
What does the overlap zone drive?
pole separation
How does the mitotic spindle get set up?
the kinesin Eg5 cross-links anti-parallel microtubules and starts pushing the centrosomes apart to form the spindle pores
the Kinesin Eg5 ______ anti-parallel microtubules and starts pushing the ________ apart to form the spindle poles
cross-links
centrosomes
Eg is also needed for ____
anaphase
Eg5 inhibition blocks _____
bipolar spindle formation
Monopolar spindle
Eg5 inhibition with moastrol prevents cetrosomes from separating in prophase and prometaphase
Anti-parallel interactions mediated by Eg5 ___ the microtubules
stabilize
Prophase to pro-metaphase transition
the nuclear envelope disassmebles at prometaphase in many species
When do the nuclear envelope and nuclear lamins reassemble?
Telophase
What does the golgi apparatus do in pro-metaphase so that each daughter cell inherits equal amounts of golgi apparatus membranes?
fragments
Secretion and endocytosis __ during the prophase to pro-metaphase transition
stop
What is the result of everything that happens during the prophase to pro-metaphase transition?
more chance of MTs growing from each centrosome contacting chromosomes quickly
Kinetochore
specialized protein structure that assembles on to the cetromere region of the chromosome in prophase
What allows the kinetochore to move along the attached MTs?
Dynein and kinesin
What is the goal of kinetochore movement?
for the two kinetochores on one chromosome to become attached to MTs coming from opposite poles
Properties of kinetochore (5)
- specialized chromosomal structure needed for spindle attachment
- binds multiple MTs at once
- microtubule bundles attached to the kinetochore can switch between growing and shrinking in regulated way
- kinetochores move in both directions along MT by harnessing MT assembly and diassembly and using dynein and kinesins
- kinetochores properly attache to MT from both poles are under tension - tension is needed before mitosis can proceed
