I. Chromosomes A.Literally translates as Colored Body B. DNA: Uncoiled, it is too thin to be seen with light microscope. C. Chromatin: DNA + Proteins 1. Histones proteins DNA wraps around (like spools of thread) 2. Nucleosome one histone wrapped with DNA. Twisted Staircase to X Kinetochore DNA Fig. 9.9, p histone core One nucleosome DNA I. Chromosomes D. The X is a condensed, duplicated chromosome. 1. The X consists of two sister chromatids (exact copies of one another) 2. Connected at centromere (constriction where microtubules can connect) D. The X is a condensed, duplicated chromosome. 3. Kinetochore the protein disc where SF actually attach I. Chromosomes Sister Chromatids, Centromere, Copies of DNA, Chromosome(s) II. Mitosis A.Purpose: To generate Two identical (Twin) nuclei. To genetically CLONE a cell. B.Where in Body? 1. Somatic Cell: Body cells (all except sperm and eggs, which are sex cells). 2. To generate DIPLOID cells (two copies of each chromosome, 2n). II. Mitosis Stages: A.Prophase: 1. Cell often loses shape (due to cytoskeleton disassemblage) 2. Nuclear membrane disintegrates. 3. DNA (sister chromatids) begins condensing. 4. Centrioles (animal cells) duplicate and move to poles of cell. 5. Spindle fibers (made of microtubule subunits) begin to assemble from each pole. Prophase II. Mitosis B. Metaphase: 1. Cell elongates as spindle microtubules overlap in middle. 2. Spindle fibers align chromosomes at equator. 3. Meta translates as middle Metaphase II. Mitosis C. Anaphase 1. Microtubules attached to centromeres shorten and pull sister chromatids apart. 2. Other microtubules grow past one another to further elongate cell. 3. Chromosomes move to poles. Anaphase Fig. 9.10, p. 157 II. Mitosis D. Telophase: (largely opposite of prophase) 1. Nuclear envelop reforms. 2. Chromsomes uncondense. 3. Spindle fibers disassemble. 4. Centrioles move from poles. Telophase II. Mitosis Final Results: Initial Final 46 chromosomes 1 cell Cell Prior to Mitosis Label ? III. Cell Cycle A.Interphase: 1. G1 (Gap 1): Normal cell growth. 2. S phase: Synthesis, DNA replicated 3. G2 (Gap 2): Cell prepares for division. B. Mitosis: Equal distribution of chromosomes into two nuclei. C. Cytokinesis: Division of cytoplasm to make two cells. IV. Cancer (Add to Notes) What is Cancer? Body cells undergoing excessive mitosis/cell division. Fig. 9.3, p. 151 Where in cell cycle? Interphase: Mitosis: IV. Cytokinesis A.Cell leaves mitosis as 1 cell with 2 nuclei! B.Cytokinesis is division of cytoplasm 1. Animal Cells: Cleavage furrow forms as cell constricts. 2. Plant Cells: Cell plate forms as two cells divide cytoplasm. light micrograph and transmission electron micrograph showing cell plate formation in a dividing plant cell cell wall former spindle equator vesicles converging cell plate Fig. 9.6, p. 154 Mitosis is over, and the spindle is now disassembling. The contractions continue and cut the cell in two. Just beneath the plasma membrane, a band of microfilaments at the former spindle equator contracts, so that its diameter shrinks all around the cell. Fig. 9.7, p. 154