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

1. Cancer cells build their own blood vessels

Metastasis of cancer cells

2. invade surrounding blood vessels

3. transported by the circulatory system to distant sites

4. invade new tissue and grow in a new location