The cell cycle Flashcards
What is required to prevent the introduction of serious errors during cell number expansion?
Coordination mechanism
What are the 3 critical events that need to occur during the cell cycle?
- Chromosome replication
- Chromosome segregation
- Cell division
What do almost all normal cells require in order to proliferate?
Extrinsic factors
What type of proteins can overrule stimulatory factors & force proliferation to a halt?
Signalling proteins
What is the master governor that makes the major decisions regarding the cell fate?
Cell cycle clock (operates in the nucleus)
What are the 2 process that the cell cycle clock can encourage?
Division or the prevention of replication (sent into G0 or quiescent state)
What are the 5 stages of the cell cycle?
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
What occurs during prophase?
movement of the centrioles to polar end of the nucleus, condensation of chromosomes
What occurs during prometaphase?
components of the mitotically spindle elongate away from the spindle poles
What occurs during metaphase?
chromosome alignment is complete
What occurs during anaphase?
pairs of sister chromatids are separated
What occurs during telophase?
chromosomes start to de-condense, nuclear membrane starts to be re-established.
When is chromatin de-condensed?
when the cell is not dividing (de-condenses after telophase)
Describe the parts of interphase
G1, S (synthesis phase), G2, M (mitotic phase)
What occurs during G1?
- cell increases in size
- ribosomes, RNA produced
- preparation for DNA synthesis
- where the cell responds to signals
What occurs during the S stage?
DNA synthesised (chromosome duplicated)
What occurs during the G2 phase?
- cell checks for fidelity of DNA
- preparation for nuclear division
What stage during interphase takes the longest time?
G1 takes the longest duration
What occurs if a cell enters G0?
They will not divide & not grow. They can re-enter the cycle from G0?
What process actually occurs during G0 phase?
cytokine removal can occur - from G1 to G2
What is the purpose of checkpoints?
- allows for increase to scheduled length of a phase.
- facilitates repair processes
What occurs at the G1 checkpoint (end of G1)?
checks for DNA damage & may rectify situation if problem is detected?
What occurs at the G2 checkpoint?
check for damage or if DNA replication is incomplete
What occurs at the M checkpoint?
check for chromosomal attachment to spindle fibres
The removal of what factors in the final hour of G1 allows for the transition into S, G2 & M phase?
serum & growth factors
The deregulation of what point in the G1 phase can lead to cancer?
R point (point of no return), where cells are sensitive to cytokine withdrawal
What staining is used to view cells at different stages of the cell cycle?
Diffuse staining
What is the problem with using the genetic approach to look for genes that bring about a cell cycle transition?
Requires cells that have a mutation in a putative cell cycle transition gene
What is the problem with using the genetic approach to look for genes that bring about a cell cycle transition?
requires supply large number of cells undertaking the same transition at the same time
What is the advantage of using yeast as a genetic model for a cell cycle?
- rapid division rate (<1hr)
- cell cycle control genes are highly conserved
- yeast can be growth as haploid or diploids
What are 2 genetic tricks allow identification of potentially lethal mutations?
- diploid can be used to maintain lethal mutations, that are then studied in haploid.
- temperature sensitive mutations allow growth at permissive temperature
What can be used to deplete the cytoplasm of different proteins during cell-free mitosis?
antibodies
What is an example of hormonal activity causing the transition to M phase?
oocyte to egg transition
What 2 classes of proteins must be present to allow transition from G2 to M?
cyclin & cyclin-dependent kinases (have to exist as a complex)
What are protein kinases?
signalling devices which operate to create molecular
Does there seem to be a relationship between kinase activity & the cell cycle transitions?
YES
What is the cell cycle regulator kinase called in yeast?
CDk1 (cyclin-dependent kinase 1), however there are multiple kinases
How do yeast cells activate transition between different stages of the cell cycle?
The presence of different cyclins, paired with CDk1 (cyclin-dependent kinase 1)
What 2 factors drive forward transition between different stages of the cell cycle?
Cyclin/CDKs
What type of cyclins are controlled by extracellular signals?
D-type cyclins
What can regulate the formation of cyclin/CDKs complexes?
CDK inhibitors (CKIs)
