Regulation Of Cell Cycle Flashcards
Why is correct regulation of cell cycle important for development?
Organs and body parts need to be correct size
Why is correct regulation of cell division important in injury?
Cells need to divide following injury but stop when damage repaired
What are the adaptive responses of cell division?
Cells in bone marrow respond to low oxygen and produce more red blood cells
Lymphocytes increase in response to antigens
What happens if regulation of cell division breaks down in any of the aforementioned process?
Cancer
What are the external signals for which cell division is regulated?
Diffusible chemical signals produced by other cells which tell cells how to behave (mitogens/ growth factors)
What are the internal signals that regulate cell division?
Chemical signals produced internally and regulates its own cell division which is present in cytoplasm (cyclin dependent kinases)
What happens in S phase cyclins in the absence of mitogens?
S phase cyclins aren’t made
What happens if they cells don’t pass through G1?
They enter G0 (quiet phase)
What do platelets releases in injury?
Platelet derived growth factor (PDGF)
What do PDGF do?
Binds to receptors on surface of skin cells and cause them to start dividing
Internal signals were first identified by fusing cells from which stages of cell cycle?
M+G2
M+G2 or S
G1+S
G1+G2
What were the conclusions of cell fusion experiments?
There is mitosis promoting factor in M phase cells
Cells at any stage of the cell can be stimulated by M phase cell to enter mitosis
What were the conclusions of the second cell fusion experiment?
There is an S phase promoting factor in S phase
Although there is an S phase promoting factor in S phase cells, only G1 cells respond to the factor
What is the role of checkpoints?
Enable cells to stop dividing if correct signals aren’t present and allow cells to be reviewed in current circumstances
When is genetic instability caused?
If a cell proceeds from one phase of the cycle to the next inappropriately
What does the G1 checkpoint check?
Is cell a suitable size?
Has it received external signals?
So commits cell to cell cycle and would proceed to S phase instead of G0
What are the checks of G2 checkpoint?
Is it a suitable size?
Is DNA replicated?
Is environmental favourable?
Cell halts here if these aren’t met
What are the checks of M checkpoint?
Are all chromosomes attached to spindles?
Who discovered cyclins?
Sir Tim Hunt
What did sir Tim Hunt observe?
Cells in sea urchins early embryos synchronously. He found a group of protein level which increased and decreased between interphase and mitotic phase
What does SPF regulate?
G1 checkpoint
What does MPF regulate?
G2 checkpoint?
What remains constant of Cdk in the cell cycle and what is enhanced by changes in cyclin levels?
Constant: expression level
Changes: their activity
What does MPF consist of?
Cdk1 and cyclin B
