BS 161 1st Edition Lecture 26 Outline of Last Lecture I. Cell cycle IOutline of Current Lecture II. Cell cycle IICurrent Lecture-cell cycle clock: engine; a series of activation and deactivation reactions of proteins (cyclins andcyclin-dependent kinases) that pace the cell cycle-G1 (start): determine if DNA synthesis should begin-G2: determine if mitosis should begin-M: determine if mitosis should be completed-cytoplasmic factors control nuclear events-the start (G1) phase is dominated by the M phase in experiments where the cells are fused together-the chromosome of the G1 cell condenses-cyclins regulate transcription and translation-cyclins are proteins, they build up during interphase and reach their peak at mitosis-cyclins bind to and activate kinase-mitosis promotion factor (MPF) is made of cyclin and cyclin-dependent kinase (CDK)-MDF functions: nuclear lamins phosphorylated, chromosome condensation, and spindle formation-some proteins can inhibit MDF-one is called P27: it inhibits the cell cycle by making the MPF not functional-P27 inhibits the inhibitor of the cell cycle-mice with P27 are larger than mice without-major phenotypic changes in cancer cells:1. loss of checkpoint controls2. immortality: cancer cells can continually divide3. loss of adhesion dependence and gain of motility -cancer cells form overlapping layer of rounded
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