Post on 04-Jan-2016
Review of the Cell Cycle
Cell cycle checkpoints (three major types of checkpoints)
1. A checkpoint insures that all DNA damage has been corrected prior to entry into S phase
2. A checkpoint insures that all DNA has been duplicated before the cell enters into mitosis
3. A mitotic checkpoint ensures that all chromosomes have been aligned on the metaphase plate before anaphase is allowed to begin
The cell cycle checkpoints can result in a cell entering apoptosis(for instance, if there is too much DNA damage to be repaired ). Apoptosis is programmed cell death that can result from signals external or internal to the cell. In either case, proteolytic enzymes called capsases are activated.
Defects in cell cycle checkpoints can lead to a variety of pathological conditions, including cancer and genetic defects.
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Click below to review or learn more about mitosis (in the cell
cycle)
Mitosis
Cell Cycle regulation
• Protein molecules called Cyclins
• CDK’s (cyclin dependent kinases)
• 2 types – Internal regulators – respond to events within
the cell (ex., no mitosis until chromosomes replicated)
– External regulators – respond to outside factors and speed up/slow down activity
Cell Cycle regulation
Click below to learn more about Cancer and the Cell
Cycle
Cancer
Cancer therapy targets components of the cell cycle. Most cancer chemotherapeutic drugs target dividing cells (and are not specific for cancer cells).
Specific targets are DNA synthesis (S phase) and mitosis (M phase).
Drugs like Methotrexate (5-fluorouracil; a nucleoside analog) and Topoisomerase II inhibitors interferes with DNA synthesis (S phase).
Drugs like vinblastine and Taxol interfere with microtubule dynamics and mitosis.
DNA damage induced by radiation and chemotherapy can induce apoptosis
"There's an industrial park's worth of molecular
machinery running the cell cycle". Paul Nurse in "The
Incredible Life and Times of Biological cells". Science 289: 1711-1716 (2000)
Happy Trails, pardner!