Transcript Document
5.3 Regulation of the Cell Cycle LEQ: Why is the eukaryotic cell cycle regulated? • Key terms: cyclin, growth factor, kinase • Reading 5.3 (cancer) 5.3 Regulation of the Cell Cycle • Activator: • Briefly explain why the daughter cells resulting from mitosis are genetically identical to each other and to the original parent cell. 5.3 Regulation of the Cell Cycle Cells respond to internal and external signals that regulate cell division. • Cell communication: • physical contact with cells • Cell signaling: – Receptors/enzymes – soluble chemical signals: - Growth factors - Survival signals 5.3 Regulation of the Cell Cycle Internal and external factors: Example • Cell adhesion (stops cycle) – Positional information to nucleus – integrins 5.3 Regulation of the Cell Cycle All cells rely on cell signaling to detect and respond to cues in their environment: – Receptor Tyrosine Kinase (RTKs) activation involves binding to a signal (ligand), the joining together and phosphorylation of proteins. – Growth promoting 5.3 Regulation of the Cell Cycle Signaling pathways • Prevent division or, • Promote cell division: – Ras pathways promote cell division by turning on genes/proteins associated with the cell cycle 5.3 Regulation of the Cell Cycle Cdks coordinate passage through checkpoints: • Checkpoints: – G1/S - Restriction/ enter S – G2/M - Enter M – Spindle/metaphase - Exit M 5.3 Regulation of the Cell Cycle • Cyclins activate Cdks • Timing of each phase can be adjusted • Failure/DNA damage can result in cell death. – apoptosis 5.3 Regulation of the Cell Cycle • Cell cycles can vary based on stages of development 5.3 Regulation of the Cell Cycle Programmed cell death purges damaged cells to prevent disease and shape development • Apoptosis is programmed cell death: – Initiation of “death” proteins (caspases) - self-destructive enzymes – Results in progressive cell destruction - animation 5.3 Regulation of the Cell Cycle Pair Question: • Suppose a mutation in a Cdk gene causes the Cdk protein to change shape so it spontaneously activates without the aid of cyclins. Predict what would happen to the cell. • Suppose a mutation in a caspase gene causes a Caspase protein to change shape so it spontaneously activates without the aid of a signaling molecule. Predict what would happen to the cell. 5.3 Regulation of the Cell Cycle • Competition in a tissue for growth factors “sculpts” a tissue – Loss of “tails” – Finger webbing webbed fingers 5.3 Regulation of the Cell Cycle • Leaf senescence (fall) is programmed cell death! • Leaf development is programmed, seasonal cell growth! 5.3 Regulation of the Cell Cycle Telomere shortening leads to senescence and programmed cell death 5.3 Regulation of the Cell Cycle