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Lecture 18

Lecture 18 - Cancer.docx

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Biology 1002B
Tom Haffie

Lecture 17: Cancer Which of the following sequences is transcribed but not translated? 1. ER target sequence 2. SD box 3. Enhancer 4. Terminator A) 1, 2 & 3 B) 2 & 4 C) 1&3 D) 4 only E) All X-Inactivation  X chromosome inactivation creates genetic mosaics o X-linked genes (dependent on which X is activated)  Xp is preferentially silenced in some tissues – imprinting o Ex. placenta  Shutting Off X o Chromosomes that are loose and available are more likely to be transcribed o Tightly Pact – RNA (Xist – x inactive specific transcript) binds along the X chromosome & most genes  Xist  Functions as RNA  Associated with X and shuts down transcription of x o Affects the whole chromosome (unlike other epigenetic mechanisms) Cancer  In Canada, men are at higher risk for cancer than women  Leading cuase of premature death in Canada  40% of women & 45% of men will develop cancer  25% of Canadians can expect to die of cancer  Rates among youth are rising Top Four  Colon (15%)  Prostate (25%)  Lung (15%)  Breast (25%) Proof that Cancer is Genetic  Can inherit predisposition to cancer – not the actual cancer  Oncogenes – mutations in these genes cause cancer  Later exposed to environmental factor that induces cancer Embryogenesis  Requires rapidly dividing cells  Cell cycle control Cell Cycle  CDK o Cylin dependent kinase o Kinase - phosphorylases and very potent regulators of protein expression o Master control switches for cell cycle checkpoints o Present all the time o Inactive until bound to respective cyclin protein  CDK – enzyme  Cyclin – protein Regulatory Protein: MPF  MPF o Maturation promoting factor o Mitosis promoting factor  When MPF level and cyclin levels peak, the cell enters mitosis Controlling Entry into Mitosis 1. A CDK is activated when combined with a cyclin and then adds phosphate groups to target proteins, activating them (MPF) 2. Activated proteins trigger the cell to progress into the next cell cycle stage 3. Each major stage of cell cycle begins with activation of one or more cyclin: CDK complexes and ends with deactivation of the complexes by breakdown of cyclins 4. When MPF levels peak, the cell enters mitosis. During anaphase, the cyclin is degraded (pulled apart into amino acids) and the CDK is recycled 5. New cyclin builds up during the next cell cycle 6. External controls are based primarily on surface receptors that recognize and bind signals such as peptide hormones and growth factors, surface groups on other cells, or molecules of the extracellular matric 7. Binding triggers internal reactions that speed, slow or stop cell division Under influence of external and internal controls, cells may actively cycle, sit in G0 or undergo apoptosis External Controls  Surface receptors that recognize and bind signals such as peptide hormones and growth factors, surface groups on other cells, or molecules of the extracellular matrix  Binding triggers internal reactions that speed up, slow or stop d
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