Cell division Flashcards
How can you identify which stage of the cycle a cell is in?
Analysis of DNA content of an asynchronous population by flow cytometry
Regulation of the cell cycle
key points is focused primarily at …?
at G1/S and G2/M transition. Relies on transient activation of a protein kinase complex (Cdk-cyclin) allowing progression through the cell cycle
cdk (cyclin dependant kinases) have subunits with ??? activity
Subunit with ser/thr kinase activity
Cyclins are a ??? subunit that attach to cdks to form a complex
regulatory subunit (concentration rises and falls)
TRUE OR FALSE: cell cycle regulation in fission yeast has two cyclins or two cdks? and only one of the other.
two cyclin types, a G1 phase cyclin, and a M phase cyclin, only one cdk known as cdc2 in yeast
are all cdk-cyclin complexes stimulatory?
No, not all cdk-cyclins are stimulatory
e.g. cyclinB1-Cdk1 has inhibitory function in G2 – prevents cells from rereplicating DNA
For cells to pass through a point of commitment (i.e checkpoints) Cdks must be transiently activated by specific ???
cyclins.
checkpoint at ??? checks whether Mitogenic signal has been received.
G1 to S phase checkpoint
If mitogenic signal has been received at G1-S phase checkpoint, what happens?
DNA synthesis machinery is triggered
TRUE or FALSE: if a mitogenic signal is not received at G1-S checkpoint, the cell doesn’t go into G0 phase i.e. terminal differentation
FALSE, it DOES go into Go
terminal differentiation time of cell spent in this phase varies. some cells like ??? never go into this phase as they are constantly differentiating/replicating/growing whilst others like ??? stay for a long time in G0
stem cells cells
neurons and RBCs
the checkpoint at ??? checks whether cell is big enough and whether DNA is replicated and undamaged
S-G2 checkpoint
passing the S-G2 checkpoint triggers ??? machinery
mitosis machinery
TRUE or FALSE: G2 is shorter than G1 and less variable due to its activity metabolically (glucose oxidation,
replication, transcription, translation)
TRUE
external factors such as ??? stimulate a cell to divide or not
cytokines, growth factors
at what stage do Centrosomes duplicate and Chromosomes start to
condense? Also cytoskeleton disassembles
G2 phase
at what stage does DNA get replicated and histones produced in higher quantities?
S ohase
at what stage of cell division do organelles get duplicated and cell grows normally and metabolism is normal?
G1 phase
Analysis of DNA content of an asynchronous population by flow cytometry reveals ???
which stage of the cell cycle a cell is in
Regulation of the cell cycle relies on transiently activated ??? which then allows progression through cycle
cdk-cyclin complex
TRUE or FALSE: Specificity of cdk action depends on type of associated cyclin binding to it
TRUE
Eg., nuclear lamins»_space; nuclear-envelope breakdown
Other proteins»_space; changes in organisation of chromosome and cytoskeleton
- cyclin binding to cdk causes conformational change that allows the active site to be exposed. The active cdk can then ??? other proteins
phosphorylate
- cyclin and cdk synthesis is important for commitment to enter cell cycle e.g. yeast divides until ???
negative nutrient signal is received. In eukaryotes this is growth factors
- steps of synthesis involve:
- growth factor binding to RTK =
- activation of Ras =
- activation of ??? pathway
- activates produciton of jun and fos (nuclear transcription factors
- ???
- MAPK
- synthesis of G1 cyclins and cdks
example of steps of cdk and cyclin synthesis is the:
G1 cdk-cyclin complex regulates progression through constriction point by ??? Rb protein which binds E2F (transcription factor)
phosphorylating
when Rb is phosphorylated and binds to E2F, transcription occurs or does not occur?
does not occur. Only occurs once Rb releases E2F upon phosphorylation by protein kinases
- controlled proteolysis via the ???
ubiquitin-proteasome pathway
- proteolysis of cdks and cyclins involves two types of ubiquitin ligase:
- ??? (active in mitosis, targets mitotic cyclin = cell exits mitosis)
- SCF complex (active from late G1, targets ??? cyclins)
- anaphase promoting complex
- G1 cyclins
Active mitotic Cdk-cyclin stimulates:
1. Nuclear envelope breakdown
2. Chromosome condensation
3. ??? formation
4. Targeted protein degradation
Mitotic spindle
- control of cdk activity by regulation by inhibitory phosphorylation:
- Y15-P = ??? until phosphotase comes along to remove phosphate group
- T161-P = ???
Y15-P = inhibitory
T161-P = activatory
- subcellular localisation:
e.g. Cyclin B1-GFP is in cytoplasm and not allowed into ??? until it is needed. This is via control of gates/shuttles across membrane/envelope
nucleus where it has its effect
- Checkpoints, Cdk Inhibitors, and
Cellular Responses: Progress through the cell cycle can be arrested
at a checkpoint by:
* Sensors that detect ???
* Transmitters that signal the information.
* Effectors that inhibit cell cycle machinery. (Eg CdK inhibitors)
chromosomal abnormalities
ATM gene generates ATM protein which repairs dsDNA breakage from ??? but when mutated does not = many dsDNA breaks
ionising radiation
