Cell proliferation Flashcards
What are the phases in Cell cycle
G1–>S–>G2–>M–>G0 (optional)
What is the G1 phase doing
Growing in cell size and preparation for DNA replication
What is S phase doing
DNA replication
What is G2 phase doing
Checking for error in DNA replication and prep for cell division
Name the 2 parts of M phase
Mitosis and Cytokinesis
What is G0
Temporary or permanent stop dividing and enter a quiscence phase
At what stage the chromosome becomesX shaped
S stage
What is the fate of the 2 chromatids
Become daughter chromosomes
What is homologous chromosomes
Pair of chromosomes that are similar in size, shape and carries gene that controls the same inherited characteristics
At which stage is the cell a diploid
G1, after replication
Other than diploid, name another state that the cell can be
Tetraploid
What are the 3 checkpoints and what do they look for
G1–>S: Environment favourable? Large enough cell size? DNA damage?
G2–>M: Large enough cell size? All DNA replicated? All DNA damage repaired?
M:All chromosomes attached to spindle fibre?
–> Pull them apart
What is the family of molecules that regulated cell cycle called
Cyclin-cyclin-dependent kinase complexes
What is the G1 cyclin refers to. Under what circumstances is it activated and what’s it’s activity. What is the significance
It means Cyclin D Ckd 4/6. It is activated to release Cyclin D when Growth factor is sufficient. It reflects the Nutrient availabilty, stress factor and growth factor
Name the tumour suppressor protein which acts on DNA. How does it work
Prb (Rb), can inhibit E2F, which is a transcription factor, hence no cyclin E can be formed to start S phase
Name the Tumour suppressor that look for DNA damage. Suggest how it works
p53. ATR ATM binds to DNA and look for DNA damage. When one is detected, it activiate Chk2 which phosphorylates p53 and separate it from MdM2 which breaks it down by polyubiquitylation, making p53 activated instead of being degraded.
It can activate p21 gene to make p21 protein which inhibit Cyclin Cdk1, Cyclin Cdk2, Cyclin Cdk 4/6
What are the signifance to pause cell cycle
To allow time for DNA repair or apoptosis
What is the S phase Cyclin
Cycin E Cdk2
How does Cyclin E Cdk2 prevent duplicating DNA twice
It phosphorylate the Cdt1 and Cdt6 on the replication bubble so that they are hyperphosphorylated and cannot function to replicate
What is the Mphase Cyclin refering to
Cyclin B Cdk1
What are the site of phosphorylation on M phase Cyclin for
Deactivating it
Name the protein activating M phase Cyclin and why it is activated only after replication
The Cdc 25 protein .
It is inhibited by Chk1 in the replication state as long as the Chk1 is activated by the ATR protein in S/G2 phase
What is the importance of Cyclin B/Cdk 1
It breaks down the intermediate filament, ie Lamin
As well as phosphorlyating the condensin to condense the chromosomes
What is the fate of it after replication
It is degraded by polyubiquitinylion
