Cell Cycle Guided Reading Questions Review MU9Y

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 G 2 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 - Cyclin dependent 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 Animation

Cell Cycle Pathways **Growth factors act as social controls** ( if deprived of growth factors cells remain in G 0 ) In normal cells: GF’s rcvd from surrounding cells bind to receptors induce cyclin production cell division initiated

In abnormal cells: G F’s not needed for growth/division p athway disrupted o verproduction 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/division ~ invasive ~ damage healthy cells ~ No controls Both ~ grow ~ divide

Mutations in the cell cycle signaling are responsible for many cancers. Image taken from: Ebook figure 10.24www.ravenbiology.com

Cancer is a disease of the cell cycle

The environment: Some environmental agents associated with cancer are: Viruses Tobacco smoke Food Radiation Chemicals Pollution

Viruses Viruses—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%.