Control of Cell Cycle
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To ensure that daughter cells are viable the parent cells cell cycle has ____ _____ to control order and timings of some transitions?
What are the three check points in the cell cycle?
- G1check point
- G2 check point
- M check point
When does the G1 check point occur?
Near the end of G1 (Interphase)
What does the G1 check point check?
The size of the cells (that they are not too small)
What will happen if a cell is too small?
It will not enter S phase. The cell will enter G0 until it is fixed.
When does the G2 check point occur?
At the end of G2 (Interphase)
What does the G2 check point check for?
It checks DNA is replicated properly
What is the G2 check point controlled by?
Mitosis promoting factor - MPF. If enough of this complex is present the cell will enter mitosis.
What does MPF promote?
MPF promotes the assembly of miotic spindle, break down of nuclear envelope and condesation of chromosomes
When does the M check point occur?
What does the M check point check?
It monitors chromosome allignment to ensure each daughter cell recieves one chromatid from each chromosome. This controls entry to anaphase and exit from mitosis/start of cytokinesis
What is cancer?
A disease where DNA is damaged, the regulation of the cell cycle goes wrong and normal growth and behaviour are lost.
What does cancer result in?
- Uncontrollable growth of undifferentiated cells
- Creation of abnormal cells
- Attraction of blood vessels to the tumor
- Cancer cells living longer than other cells
What type of genes encode proteins which stimulate cell division in a regulated manner when required eg to heal a wound?
Proliferation genes or proto-oncogenes
If proto-oncogenes mutate what do they become?
What can oncogenes cause?
Unregulated excessive cell division / tumor formation
How many proto-oncogenes need to mutate for excessive cell division to occur?
What are antiproliferation genes / tumor suppressor genes?
These are genes which encode proteins which restrict cell division at cell cycle check points
How many mutations needs to occur before they stop preventing cells growing uncontrollably?
What is an example of a tumor suppressor gene?
When cells differentiate they become...?
Cells can be organised into tissues and then...?
Cellular differentiation depends on changes in _______ _______ resulting in genes being switched on and off?
The more specialised the cell the ______ the genes switched on?
What kind of cells maintain the capacity to use most genes?
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