cell cycle guided reading questions review mu9y
Post on 26-Dec-2015
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Cell Cycle Guided Reading Questions
Review
https://www.youtube.com/watch?v=xukDIWFMU9Y
Just a few facts!
Intestinal cells- divide more than 2X day
Nerve and muscle cells- never divide always in GO
Human liver- divides 1X year but will divide more if needed for repair
Mitosis Promoting Factor (MPF) low in early G2 rising throughout the phase and peaks in mitosis
2 subunits:1.Protein kinase –
[constant]; catalyzes phosphorylation
2.Cyclin – [increases]; regulatory proteins that binds to kinase
Cdk -Cyclindependent kinase
**Dimer activates MPF
Activated MPF initiates production of several proteins (G2 phase)
a) Chromosomal proteins – initiates M phase
b) Lamins –initiates breakdown of nuclear envelope (fibrous proteins)
c) Microtubule associated proteins – activate mitotic spindle?
d) Enzyme degrading cyclin – deactivate MPF
• sufficient nutrients• GF’s (growth
factors) present• DNA undamaged•Size of cell
Cell Cycle Regulated by 3 checkpoints(controlled by Cdk enzymes)G1/S Checkpoint
G2 /M Checkpoint
•DNA undamaged
Spindle (Metaphase )Checkpoint
Cell Cycle Control Animationhttps://www.youtube.com/watch?v=JcZQkmooyPk
Cell Cycle Pathways
**Growth factors act as social controls**(if deprived of growth factors cells remain in G0)
In normal cells:• GF’s rcvd from surrounding cells bind to receptors
• induce cyclin production
• cell division initiated
In abnormal cells:• GF’s not needed for growth/division
• pathway disrupted• overproduction of cyclin (↑ division)• defective “brake proteins” can not suppress growth → tumors • benign• malignant (metastasis)
•Oncogenes- the gene that when mutated or in abnormal increased levels can promote unregulated stimulated growth (contribute to cancer)
Stages of Mitosis Animation
Healthy Cells
~ normal growth~ GF’s
~ Adhere to nearby cells~ Regulation
Cancerous Cells
~ Rapid growth/divisi
on~ invasive ~ damage
healthy cells~ No controls
Both~ grow~ divide
Mutations in the cell cycle signaling are responsible for many cancers.Image taken from: www.ravenbiology.com Ebook figure 10.24
Cancer is a disease of the cell cycle
The environment:
Some environmental agents associated with cancer are: • Viruses • Tobacco smoke • Food • Radiation • Chemicals • Pollution
VirusesViruses—mostly in the form of DNA viruses—have been causally linked to cancer.
• human papillomaviruses—primarily types 16 and 18, which are sexually transmitted—have been linked to cervical cancer;
• more than 25 other types of papillomaviruses have been linked to cancer as well
• hepatitis B and C—linked to cancer of the liver • human immunodeficiency virus (HIV)—linked to Kaposi's
sarcoma and lymphoma • retroviruses—linked to cancers in animals other than
humans
Tobacco smoke
• is associated with 50% to 60% of all cancer deaths• is causally linked to cancers of the lung, upper respiratory
tract, oesophagus, bladder, pancreas • is probably a cause of cancer of the stomach, liver,
kidneys, colon, and rectum
Pollution
Pollution has been difficult to document as a contributor to human cancer.
However, long-term exposure to high levels of air pollution may increase lung cancer risk by as much as 25%.
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