Download - The Cell cycle: Mitosis
The Cell cycle: Mitosis
http://www.youtube.com/watch?v=C6hn3sA0ip0
At what stage do the chromosomes line up in the center of the cell?
A. ProphaseB. MetaphaseC. AnaphaseD. Telophase
A. B. C. D.
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When do the microtubules retract and pull the sister chromatids to opposite poles of the cell?
A. ProphaseB. TelophaseC. MetaphaseD. Anaphase
A. B. C. D.
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Cell cycle control and mutation
• Normal cells halt at checkpoints – proteins survey the condition of the cell
• Cancer cells skip these checkpoints
• DNA can be physically damaged, or undergo mutation– changes the structure and function of the protein coded by
the DNA– mutations may be inherited, spontaneous or caused by
carcinogens
Cancer cells skip checkpoints due to DNA damage
How can DNA damage happen?
A. Exposure to carcinogensB. Exposure to radiationC. Replication errorsD. All of the above
A. B. C. D.
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• Mutations often occur in proto-oncogenes – genes that code for cell cycle control proteins and regulatory proteins
Stimulates cell division when conditions are RIGHT
OVER-stimulates cell division when conditions are WRONG
• Tumor suppressor genes – stop cell division if conditions are not favorable– When mutated, can allow cells to override checkpoints
Stops cell division Fails to stop cell division
Example tumor suppressor gene:• BRCA1: repairs DNA breaks
– mutations that inactivate BRCA1 are associated with breast and ovarian cancers
Example proto-oncogene:• HER2: senses growth factors and activates cell division
– Mutations that activate HER2 are found in many aggressive breast cancers
Mutations in these are associated with Hereditary Cancers
A single mutation is not sufficient for the development of cancer
• Multiple hit model – process of cancer development requires multiple mutations
• may be inherited (familial risk), most are probably acquired
Cancer progression
• Angiogenesis – tumor gets its own blood supply by making blood vessles
• Loss of contact inhibition – cells will now pile up on each other
• Loss of anchorage dependence – enables a cancer cell to move to another location