Cell cycle and mitosis Flashcards
what is the difference between karyokinesis and cytokinesis?
karyokinesis: nuclear division
cytokinesis: cytoplasmisc division
what is the difference between apoptosis and necrosis?
Necrosis:
- small blebs form and the structure of the nucleus changes
- the blebs fuse and become larger
- the cell membrane ruptures and releases the cell’s content
Apoptosis:
- small blebs form
- nucleus breaks apart and the DNA breaks into small pieces
- cell breaks up into several apoptic bodies
difference:
-in necrosis no organlles are located in the blebs, where as in apoptosis they are and are still functioning
what happens in the G1 phase?
lasts for 8-10 hours
- Cells don’t pass G1 without growth factors
- High rate of metabolism
- Protein synthesis
- Vigorous growth
- Duplicates most organelles
- Centrosome replication begins
what happens in the S phase?
- last for 2 hours
- dna replicates
- Synthesis of new histones.
- Assembly of new chromatin
what happens in the G2 phase?
lasts for 4-6 hours
- Synthesis of enzymes and proteins essential for cell division
- Replication of centrioles completed (form the spindle apparatus associated with the movement of DNA)
what is the kinetochore?
•the protein structure on chromatids where the spindle fibres attach during cell division to pull sister chromatids apart
how does the contractile ring form?
The actin cytoskeleton contracts, creating a cleavage furrow between the two cells. This continues until distinct membranes are formed.
what are hematopoietic stem cells?
cells that continually divide in the adult human
what is a check point?
A checkpoint is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable.
when do checkpoint occur?
G1 checkpoint; Damage to DNA and other external factors
if conditions are inadequate, the cell will not be allowed to continue to the S phase of interphase.
G2 checkpoint; ensures all of the chromosomes have been replicated and that the replicated DNA is not damaged before cell enters mitosis.
M checkpoint: determines whether all the sister chromatids are correctly attached to the spindle microtubules before the cell enters the irreversible anaphase stage.
how do cyclins regulate the cell cycle?
Through phosphorylation, Cdks signal the cell that it is ready to pass into the next stage of the cell cycle.
how are onco genes similar to mutated tumour suppressor genes
they both cause an unrestrained cell cycle and prevent apoptosis from occuring
Oncogenes:
excess cyclin –> unrestrained cell cycle
excess inhibitors of p53 –> apoptosis does not occur
mutated tumor supressor genes
no inhibitors of cyclin –> unrestrained cell cycle
no promoters of p53 –> apoptosis does not occur
what is p53?
a gene that codes for a protein that regulates the cell cycle and hence functions as a tumor suppression
how to mitotic inhibitors work?
•Affect microtubules the M phase of the cell cycle
vinca alkaloids prevent microtubule assmebly
taxanes prevent microtubule disassembly
