Cell cycle control Flashcards
what is the length of cell cycle?
in embryonic cells its 2hrs
in adults its around 20-24hrs
some cells are permanetly arrested at G0 e.g. nerves, muscles
what occurs at interphase G1?
-cells grow and doubles the number of organelles
cell increase in size
what occurs in interphase G2?
- cell increases in size again
- produce lots of tubulin
- centrosome is duplicated and both copies remain together on one side of the nucleus
what are the 3 classes of spindle microtubles?
1-astral, contribute to pole seperation
2-kinetochore, attach to kinetochore on duplicate chromosome
3-overlap microtubules (interpolar), overlap at the equator and responsible for bipolar shape of the spindle
where are mitotic spindle made?
in the microtubles
what occurs during phase S?
-DNA replicates and each chromosome duplicates
what is the effect of drugs on mitotic spindle?
they’ll stabilise them or destabilise them
what are the different types of microtubule motor proteins?
kinesins- walk towards the positive end
dyneins- move towards the negative end of the microtubule
what are the stages in mitosis?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
- cytokinesis
what occurs during prophase?
the replication chromosomes condense
- mitotic spindle assembles between the 2 centrosomes which begin to move apart
- the aster and over MTs
what occurs during prometaphase?
- breakdown of the nuclear envelope
- random probing MT encountering a chromsome will bind to it and will eventually attach to the kinetochore
what occurs during metaphase?
- Kinetochore MT’s attach sister chromatids to opposite poles of the spindle
- chromosomes align along the equator of spindle
what occurs during anaphase?
- sister chromatids separate and pulled to each pole
- kinetochore MT’s shorten by depolymerisation
- interpolar MT’s grow and push spindle further apart
- astral MT’s pull the spindle pole versus the cell periphery attaching to the cell cortex
what occurs during telophase?
- sister chromatids arrive at each pole
- nuclear envolpe starts to reform around them
- cyctoplasm begins to divid with the formation of the contractile ring
what occurs during cytokinesis?
- myosin accumulates and begins to form a contractile ring with actin
- the cytoplasm divides by the contractile ring
- each daughter cell will receive a complement of organelles
how do cells control the activity of their proteins?
via phosphorylation/ dephosphorylation
what are the 2 other ways proteins can be switched off?
- binding to an inhibitory protein that keeps it inactive
- by targeting for degradation by attaching an ubiquitin so the protein goes to the proteasome for recycling in the cell
what are the 3 proteins that help control the cell cycle?
- cyclins
- cyclin dependant kinases
- cyclin kinase inhibitors
during what phase in the cell cycle is the amount of cyclin increasing ?
during interphase G1/2)
how are cyclin dependant kinase activated?
-by cyclin attaching to it and going through a number of phosphorylation
what are the 2 types of cyclin kinase inhibitors?
- INK CDK inhibitors
- KIP/CIP inhibitors
what are the cell cycle checkpoints?
- replication of DNA
- chromosome segregation
- continue proliferation
- DNA damage checkpoint
what needs to occurs during replication of DNA and what phase does it occur in?
- happens in S phase
- controlled by S-CKD complex
- cyclin A bound to CDK2
what needs to occurs during chromosome segregation and what phase does it occur in?
- happens at M phase
- controlled by M-CDK
- cyclin B needs to be bound to CKD1
what needs to occurs during continue proliferation and what phase does it occur in?
- happens in progression from G1 to S
- controlled by G1-CDK
- cyclin D needs to be bound to CDK 4 and 6 and Rb
what needs to occurs during DNA damage checkpoint and what phase does it occur in?
-happens during progression from G1 to S
what triggers DNA replication to occur?
S-CDK triggers DNA replication recruiting DNA polymerase and blocks rereplication CAUSING BREAK DOWN AND DEGRATION OF cDC6
what does M-CDK complex do?
- inhibits mitosis if DNA replicataion is incomplete
- triggers chromosomes to condense
- triggers the phosphorylation of proteins in the MT to become stable
- -triggers nuclear envelop breakdown
