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outline2 - UNIT 2 GENETICS How cells Reproduce I....

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UNIT 2 GENETICS How cells Reproduce I. Reproduction A. Asexual reproduction – One parent 2 identical offspring 1. Who uses it? a. prokaryotes b. single celled eukaryotes (protists, yeast) c. some multicellular organisms (plants, starfish) d. some somatic cells (body cells) in multicellular organisms 2. Consequence- All offspring are genetically identical (bacteria in lungs multiply) B. Sexual reproduction – 2 parents offspring that are NOT identical to either parent II. Eukaryotic Cell Cycle-(2 phases) A. Interphase –3 subphases: (90% of cells time in interphase) 1. G1 (Gap 1) before DNA synthesis a. cell increases/duplicates the organelles b. growing in size 2. S ( Synthesis ): DNA replication (copy necessary) a. chromosomes replicate and remain joined at their centromeres (middle of the chromosome) = sister chromatids (identical) alone = chromosome, duplicated = chromatid b. continued growth of the cell 3. G2 (Gap 2) after DNA synthesis a. protein synthesis (getting ready for division) 1
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b. general metabolic activity (ATP is available) B. Mitosis (M)- 4 subphases: 1. Prophase a. DNA – condensing (starting to become visible under light microscope), coiling more b. Nuclear envelope and nucleolus- begin to break up and disappear c. Spindle – begins to form (made up of microtubules) One end of spindle joined to: one sister chromatid at its kinetochore at the centromoric region Other end of spindle joined to: pole at microtubule organizing center (MTOC) or centrioles = animal cells d. Sister chromatids (replicated chromosomes) move – towards the center of the cell (equator) 2. Metaphase “middle” a. Sister chromatids – at the metaphase plate (equator) b. Spindle – fully formed Some spindle fibers at the equator are not attached to chromatids, what are they attached to? Attached to other spindle fibers from the opposite pole c. Nuclear envelope – disappeared 3. Anaphase a. Sister chromatids – separate (called chromosomes again) b.Spindles shorten – those joined to chromosomes c. Spindles lengthen – those joined to opposing spindle fibers (egg shape) 2
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4. Telophase/Cytokinesis – begins once all chromosomes at spindle poles a. DNA – uncoils (becomes less visible) b. Nuclear envelopes and nucleoli- reappear (2 each) c.Spindle – disappear d. Cytokinesis “splitting of the cytoplasm” 1. animals : cell at equator form two identical cells (called cleavage) 2. plants – cell plate formation. Vesicles of cellulose align and fuse at the equator (2 cells) – can’t pinch because of cell wall PRACTICE: To the left is a picture of the chromosomes of a cell in G1 of the cell cycle. Draw what this cell will look like at: 1) G2 2) Metaphase 3) After cytokinesis 4
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Meiosis and Sexual Reproduction Definitions/Terms to get started: Gamete – a sex cell (sperm, egg) Somatic cell- any cell that is not a gamete (skin cell, brain cell, etc) Homologous chromosomes – two chromosomes that are nearly identical (one inherited from mom,
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This note was uploaded on 03/21/2008 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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outline2 - UNIT 2 GENETICS How cells Reproduce I....

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