Lecture 14 Flashcards
In chromosome packing, what does the interphases chromosomes look like?
- “beads on a string”
- chromatin fiber packed nucleosomes
In chromosome packing, what do mitotic chromosomes look like?
- chromatin fiber folded into loops
- entire mitotic chromosome
What is the net result of chromosome packing
Each DNA molecule has been packaged into a mitotic chromosome that is 10,000 Fold shorter than its fully extended length
What occurs during the nuclear envelope breakdown during mitosis?
- Nuclear lamins form dimers and polyerize to form intermediate filaments
- serine residues of lamins are phosphorylated by M-Cdk
- Phosphorylated lamins depolymerize which leads to disintegration of lamin meshwork
- Nuclear envelope fragments into vesicles
What ties together the sister chromatids in M phase?
Cohesion
What needs to happen to form the mitotic spindle?
The centrosome has to be duplicated
What is the microtubule system that forms between the two centrosomes?
spindle
What do the ends of the microtubules attach to?
the kinetochores of the sister chromatids
What do the spindle function in?
High fidelity segregation of chromosomes
What happens after metaphase?
The ubiquitin ligace APC is activated which leads to the ubiquination and degradation of securing
What is the results of activated ligace APC?
the active separate cleaves cohesion which initiates anaphase
What pulls chromosomes to the centrosomes?
Microtubule shortening
Where do microtubules disassemble?
At kinetochores
What helps move the microtubules towards their spindle pole?
Shortening of kinetochore microtubules, forces are generated at kinetochores
What initiates cytokinesis?
contractile ring made of acting filaments and myosin motors
What is responsible for membrane abscission
ESCRT lll / Vps4: contractile ring
Why is the regulation of CDKs important
to pause the cell cycle until the cell cycle problem is solved
What occurs at the spindle assembly checkpoint?
- Mad2 associates with kinetochore until microtubule attachs
- Mad 2 binds to Cdc20 and prevent APC activation
- When microtubule attach to kinetochore Mad2 is released and Cdc20 can bind to APC to ubiquitinate securin (anaphase), which leads to the cleaving of the cohesion rings and the separation of the sister chromatids
What initiates DNA damage checkpoint?
p53
Cdk inhibitor p21 blcoks what
cell cycle until DNA damage is repaired
What happens if DNA damage cannot be repaired
p53 will come in and induce apoptosis
