Cell division and cell cycle Flashcards
Describe interphase
Duplication of decondensed chromosomes
Describe prophase
Two centrosomes appear
Chromosomes condense to 2 sister chromatids
Kinetochores form
Mitotic spindles form
Describe prometaphase
Chromosomes move in active motion
Fragments of nuclear envelope are present
Kinetochore microtubules are formed
Describe metaphase
2 spindle poles are present
Chromosomes line up in a mid-line plane between the 2 poles
Describe anaphase
Kinetochore shortens
spindle poles move outward
daughter chromosomes separate between the 2 poles
Describe telophase
Daughter chromosomes are present at spindle poles
contractile ring forms in center
Nuclear envelope reassembles around each daughter chromosome bundle
How long does telophase take?
~5 hours
Describe cytokinesis
Completed nuclear envelope surrounds deconsensing chromosomes
Contractile ring creates deep cleavage furrow
Reformation of interphase microtubules and centosome
What are permanent cells?
Cells that exit the cell cycle and cannot come back.
Non-renewable
What are stable cells?
Cells that exit the cell cycle but may come back if necessary
Where would stable cells enter the cell cycle?
G0
What is G1 of the cell cycle?
Growing phase (Interphase)
What is S of the cell cycle?
DNA synthesis phase (Interphase)
What is G2 of the cell cycle?
Growing phase (Interphase)
What is M of the cell cycle?
Nuclear and cellular division (Mitosis)
What is an example of a permanenet cell? Stable cell?
Hair cells in ear
Nerve cells
Parenchymal cells in liver
Smooth muscle cells
Cells that continuously divide are called what kind of cells?
Labile cells
Name 2 examples of labile cells
Epithelium, hematopoietic cells
What is the big problem with the proliferative potential of stem cells?
Getting stem cells to differentiate the right amount in the right place (and not cause cancer)
How do epithelium cells of the GI tract differentiate?
Epithelial cells differentiate from stem cells and migrate to the top of the villi
The are shed from the villi in ~5 days
Inhibition of what arachidonic acid derivative will induce loss of gut integrity?
COX-1
Is it common for cells to need more than one growth signal to initiate growth?
Yes
Can hormones act as growth factors? If yes, name 3 of them
Yes
Estrogen
Testosterone
Norepinephrine (exercise)
What are the check points of the cell cycle?
G1/S check point
G2/M check point
M check point
What is does the G1/S check point ensure?
Appropriate growth signal
Cell size
Environment
DNA
If there was no G1/S check point and a reduction in nutrition, what would happen to cell division?
Cells shrunken from malnutrition would divide
What does the G2/M check point ensure?
DNA duplication after S phase is okay
Cell size
What does the M check point ensure?
Chromosomes are correctly distributed
Describe the check points necessary for Cyclin-dependent-kinase activity
Has specific phosphate been removed?
Has specific phosphate been added?
Is cyclin present?
If yes, then output
Describe the Cyclin D G1/S check point pathway
pRB holds transcription factors inactive
Growth signals cause transcriptions of cyclins* A,B,D
Cyclin-dependent kinase forms complex with cyclin D*
CDK-cD complex phosphorylates pRB
Phosphorylation of pRB releases transcription factors
Transcription factors induce transcription of proteins necessary for chromosome duplication (S phase)
What is pRB? What cancer is it associated with?
retinoblastoma protein
Eye tumors
When are concentrations of cyclin and CDK-cyclin complex at their highest?
During mitosis
Describe the pathway that blocks cyclin D at the G1/S check point
Cell senses injury
Cell transcribes p53
p53 inhibits cell cycles and instead induces transcription of repair enzymes
How does p53 inhibit cell cycle?
p53 inhibits the growth signals that activate the cyclin D-cyclin-dependent-kinase complex
Is p53 inhibition of the cell cycle permanent?
No, only until the cell is repaired
