BOLOGY 107 Lecture 19Outline of Last Lecture I. ChromosomesII. Mitosisa. Structures formedb. Stages c. Alternatives Outline of Current Lecture III. CytokinesisIV. Cell Cycle ControlV. Meiosis Current LectureCytokinesis1) Division of two cell bodies2) Animals a) Actin forms contractile fibers around the cell, myosin contracts the actin until thecell is cut in half 3) Plants a) Vesicles containing the components of the cell wall move to the center and fuse to form new wallCell Cycle Control4) Checkpoints a) G1checkpointi) Decides if the cell continues through the cell cycle, goes into stasis, or is differentiated(1) Decision is based on if there are enough materials for the cell to continue on and if the cell is needed for divisionb) G2 checkpointi) Another check to see if there are enough materials to continue the cyclec) M checkpointi) A stasis until the chromosomes reach the metaphase plated) The checkpoints are triggered by alterations in regulatory proteinsi) Balance between stimulators and repressorsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.e) Cancer i) Failure of appropriate cell control(1) Transformation- loss of contact inhibition, immortalizationii) Benign cancer- uncontrolled growth in a localized areaiii) Malignant cancer- cancer cells enter circulation, spread and attach around the body(1) Metastasis- new tumor formed from this processMeiosisf) Homologous chromosomes- same set of chromosomes, one from each parent5) Two constructive nuclear divisionsa) Create gametes (haploid, n)b) Used in reproduction only, when fertilized, create a zygotec) Chromosomes duplicate in S phased) Meiosis I (similar to mitosis steps, differences listed)i) Prophase I(1) Physical pairing of homologous chromosomes(2) Crossing over- extra contact points switch DNA and form chiasmataii) Metaphase I(1) Same as in mitosisiii) Anaphase I(1) Chromosomes assort randomly and separate in their chromatid pairsiv) Telophase I(1) Chromosomes don’t de-condensev) Two cells formede) Meiosis IIi) The two cells undergo the same steps just as mitosis, no changes other than that the chromosomes are already duplicatedii) The chromatid pairs separate. iii) Results in four daughter cells, each
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