Student_Outline_Unit_2_Starr

Student_Outline_Unit_2_Starr - UNIT 2 GENETICS How cells...

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UNIT 2 GENETICS How cells Reproduce I. Reproduction A. Asexual reproduction – one parent > offspring identical to parent and each other 1. Who uses it? a. prokaryotes (bacterium) b. single-celled eukaryotes (protests i.e. amoeba; yeast (fungi) c. some multicellular organisms d. somatic cells (body cells; includes non sex cells; i.e. skin) (*all cells except sex/germ cells*) 2. Consequence- all offspring are genetically identical B. Sexual reproduction – two parents > offspring are not identical to either parent II. Eukaryotic Cell Cycle-(2 phases) A. Interphase –3 subphases: 90% of its time in this phase 1. G1 (Gap 1) gap before DNA synthesis 1
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a. increase in the supply of organelles (new cell needs new endomembrane system, etc. so copies are made b4 division) b. general growth (size of parent cell increases) 2. S ( Synthesis ): subphase that stands for DNA synthesis a. each chromosome that exists in the cell replicates and each one remains joined to its sister chromatid (copies remain joined to original = sister chromatids > joined at the center of the chromosomes called the centromere) b. general growth of cell 3. G2 (Gap 2) gap after DNA synthesis a. a lot of protein synthesis (a lot of tubulin produced to form spindles that chromosomes are going to move along) b. general metabolic activity (ATP production for energy of division) B. Mitosis (M)- 4 subphases: 1. Prophase a. DNA –its already replicated and it condenses (coils more); becomes visible in the light microscope b. Nuclear envelope and nucleolus- break up and begin to disappear so that the chromosomes can freely move around the cell c. Spindle – made of microtubules begins to form; 2
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One end of spindle joined to: the kinetochore at the centromere; a complex of proteins at the centromere that bind the tubulin Other end of spindle joined to: the pole of the cell d. Sister chromatids (replicated chromosomes) move – towards the equator of the cell 2. Metaphase “midway” a. Sister chromatids – now at the equator (metaphase plate) b. Spindle – is completed (joined to each chromatid and pole) Some spindle fibers at the equator are not attached to chromatids, what are they attached to? Other fibers from the opposite pole of the cell. c. Nuclear envelope – completely gone 3. Anaphase a. Sister chromatids – separate from each other (chromosomes again) b.Spindles shorten – (the ones attached to each chromatid) 3
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c. Spindles lengthen – (the ones attached to opposite spindles) – cell elongates but the chromosomes move to the poled; pulled apart 4
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4. Telophase/Cytokinesis – begins once all chromosomes at spindle poles a. DNA – uncoils again b. Nuclear envelopes and nucleoli- reappear (2 of each on opposite sides of elongated cell) c.Spindle – disassembles d. Cytokinesis (how the cytoplasm divides) 1. animals – cleavage > microfilaments form a ring around the center and ‘pinch’ the cell into two 2. plants – cell plate formation > fusion of cellulose- containing vesicles across center of cell
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This note was uploaded on 12/08/2008 for the course BIOL 101 taught by Professor Hogan during the Spring '08 term at UNC.

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Student_Outline_Unit_2_Starr - UNIT 2 GENETICS How cells...

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