cell cycle

Question 1

describe cells in G1 of interphase

Answer 1

cell growth and chromosome replication 
high amount of protein synthesis 
cell doubles in size 
cells grow and function normally 
lasts 5-6 hours

Question 2

describe cells in G0 phase

Answer 2

quiescent stage
dormant
can remain here for a long period of time
no cell proliferation but still metabolically active

Question 3

what are checkpoints controlled by?

Answer 3

protein kinases:

cyclins and cdk1

Question 4

how do cyclin levels fluctuate during the cell cycle?

Answer 4

Tim Hunt

gradually rises during interphase and then falls during mitotic phase

Question 5

what regulates the transition from G2 to M

Answer 5

maturation promoting factor

Question 6

maturation promoting factor structure

Answer 6

cyclin B and Cdk1 dimer

Question 7

cells in G2 phase

Answer 7

DNA not condensed
chromosomes duplicate
cohesins hold chromosomes together 
centrosomes duplicate
lasts 4-6 hours

Question 8

explain maturation promoting factor activation

Answer 8

Cdk1 and cyclin B join to form a dimer
Cdk1 contains the amino acids threonine 161, tyrosine 15 and threonine 14
threonine 161 is phosphorylated by Cdk activating kinase
tyrosine 15 and threonine 14 is phosphorylated leading to an accumulation of inactive Cdk1
threonine 14 and tyrosine 15 are dephosphorylated by Cdc25C forming active MPF

Question 9

what catalyses the phosphorylation of tyrosine 15?

Answer 9

Wee-1

Question 10

what happens to MPF when it leaves M phase?

Answer 10

proteolytic degradation of cyclin B by APC/C

dephosphorylation of threonine 161

Question 11

what does MPF activate in M phase?

Answer 11

mitotic protein kinases:
polo-like kinase
aurora kinase

Question 12

functions of MPF in M phase

Answer 12

chromatin condensation
nuclear envelope breakdown
fragmentation of golgi apparatus
spindle formation

Question 13

types of microtubules

Answer 13

kinetochore microtubules
chromosomal microtubules
interpolar microtubules
astral microtubules

Question 14

aneuploidy definition

Answer 14

when one daughter cell ends up with more chromosomes than the other
it can then develop into a tumour

Question 15

spindle assembly checkpoint criteria

Answer 15

microtubules are attached to kinetochore
microtubules attached with proper amount of tension which can only occur when chromosomes are properly aligned at metaphase plate

Question 16

what happens when spindle assembly checkpoint criteria are not met?

Answer 16

Bub and Mad proteins can interact with kinetochore to form a mitotic checkpoint complex (MCC)
MCC then binds with Cdc20 and inhibits APC/C and anaphase does not occur

Question 17

what happens when spindle assembly checkpoint criteria are met?

Answer 17

MCC does not form and Mad/ Bub complex dissociates from kinetochore
Cdc20 is now activated and can interact with APC/C
APC/C causes degradation of cyclin B and securin
securin is bound to separase and when securin degrades separase is activated
this causes the degradation of cohesin which allows anaphase to occur