Chapter 12: The Cell Cycle AP Biology Chapter 12: The Cell Cycle

Checkpoints (Is all going according to plan?)

Relative concentration . M G1 S G2 M G1 S G2 M MPF activity Cyclin Relative concentration Time Fluctuation of MPF activity and cyclin concentration during the cell cycle

Molecular mechanisms that help regulate the cell cycle . G1 Cyclin S Cdk Degraded cyclin M G2 accumulation G2 checkpoint Cdk Cyclin is degraded Cyclin MPF Molecular mechanisms that help regulate the cell cycle

Chromosome movement Kinetochore Tubulin subunits Motor Microtubule . Chromosome movement Kinetochore Tubulin subunits Motor protein Microtubule Chromosome

Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). 25 µm Normal mammalian cells

Cancer cells do not exhibit anchorage dependence . Cancer cells do not exhibit anchorage dependence or density-dependent inhibition. 25 µm Cancer cells

Malignant cancer cells from the breast (See the ABNORMAL “crab” shape of the cells.)

Mutations and Cancer MUTATION Cell cycle-stimulating pathway NUCLEUS Growth factor MUTATION Hyperactive Ras protein (product of oncogene) issues signals on its own G protein Cell cycle-stimulating pathway Receptor Protein kinases (phosphorylation cascade) NUCLEUS Transcription factor (activator) DNA Gene expression Protein that stimulates the cell cycle Cell cycle-inhibiting pathway Protein kinases MUTATION Defective or missing transcription factor, such as p53, cannot activate Active form of p53 UV light DNA damage in genome DNA Protein that inhibits the cell cycle

Question: Lectins are naturally occurring plant proteins that help promote increased mitosis within plant root tips. These proteins influence the normal production of MPF within the root cells and thereby speed up the cell cycle. In no more than three sentences, state ONE similarity and TWO differences between Lectin influenced cells and cancer cells. (5 Points)  

Scoring Rubric: 1pt. Discussion of one similiarity Possible discussion points: Increased cell cycle rate. Cyclin production rate is altered. 1pt. Discussion of difference number 1 1pt. Discussion of difference number 2 Possible discussion points: Cancer does not respond to checkpoints. Cancer does not have density dependent. Cancer does not have anchorage dependence. Cancer not normal function for cells. Cancer affects normal cyclin production. Cancer being caused by carcinogens, etc. 1pt. Correct use of scientific terms. 1pt. Answer has no more than three sentences. (Following Directions.)   This question addresses Essential Knowledge: 2.D.3