1. 5.3 Regulation of the Cell Cycle LEQ: Why do some eukaryotic cells have genes that encode information for cell death? Reading: 5.4, 28.1 Project day wed, fri Activator – remember mitosis? –One important observation from your group about the cell cycle from mitosis lab. –Write on left board Key terms: apoptosis, cancer, metastasis

2. 5.3 Regulation of the Cell Cycle Apoptosis is programmed cell death: –Initiation of “death” proteins (caspases) -self-destructive enzymes –Results in progressive cell destruction -animation

3. 5.3 Regulation of the Cell Cycle Volvox parental colony commits suicide – why?

4. 5.3 Regulation of the Cell Cycle Competition in a tissue for growth factors “sculpts” a tissue –Loss of “tails” –Finger webbing webbed fingers

5. 5.3 Regulation of the Cell Cycle Leaf senescence (fall) is programmed cell death! Leaf development is programmed, seasonal cell growth!

6. 5.3 Regulation of the Cell Cycle A network of genes controls development, aging and the cell cycle Tissues are “sculpted” using molecular signals: –growth promoting –death promoting Changes in gene expression/signaling –Abnormal development –aging –disease

7. 5.3 Regulation of the Cell Cycle A subdermal fat layer, middle, in a mouse purged of senescent cells. These mice can run much longer and have larger fat deposits

8. 5.3 Regulation of the Cell Cycle Fat ebbs during aging when senescent cells remain. Research raises the possibility that attacks on the cells could postpone diseases of aging.

9. 5.3 Regulation of the Cell Cycle Fig. 47-25a Apical ectodermal ridge (AER) Limb buds Posterior Anterior Limb bud AER ZPA 50 µm

10. 5.3 Regulation of the Cell Cycle Fig. 47-25b Digits Anterior 2 3 4 Posterior Ventral Distal Dorsal Proximal

11. 5.3 Regulation of the Cell Cycle Fig. 47-26a Host limb bud Posterior Anterior New ZPA EXPERIMENT ZPA Donor limb bud

12. 5.3 Regulation of the Cell Cycle Fig. 47-26b 2 3 4 RESULTS 2 3 4

13. 5.3 Regulation of the Cell Cycle How did wing-building change when the cells of the ZPA were transplanted? Speculate: how do the cells of the ZPA make wing patterns form?

14. 5.3 Regulation of the Cell Cycle Cyclopia is caused by mistake in signals that coordinate cell division across tissues –Sonic hedgehog (signal, ligand)

15. 5.3 Regulation of the Cell Cycle Cyclopia can be caused by intake of cyclopamine during pregnancy –Teratogen –disrupts the Sonic hedgehog signal Sonic Hedgehog regulates: –brain/face development –Wing-building –Cell division of nervous, connective tissues

16. 5.3 Regulation of the Cell Cycle Summary: How does cell cycle regulation assist in the homeostasis of tissues? Speculate: why were so few cells observed actively undergoing mitosis in onion root tips/fish blastulas?