B6A3CellCyclesF09

B6A3CellCyclesF09 - Cell Cycles & Life Cycles The DNA...

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Heyer 1 The DNA Gene Theory The DNA Gene Theory 1. DNA is the molecule of inheritance. 2. A chromosome is one long dsDNA. ÿ In eukaryotes, the dsDNA molecule is wrapped chromatin . 3. A gene (a discrete unit of heredity) is a specific region of DNA on a chromosome. ÿ Specific gene: instructions for a specific protein 4. Each chromosome = 100s–1000s of genes. The Cell Theory The Cell Theory Cell Doctrine Cell Doctrine 1. All organisms are constructed of one or more cells. 2. The cell is the basic unit of life. 3. All cells arise from previous cells. Omnis cellula e cellula ! \ cellular reproduction must include Cellula Cellula V – New cells produced – Need the right number of cells in the right location • Either too few or too many is bad. V Cell Replacement – Lost or damaged cells replaced V Asexual Reproduction – New organism formed Sea star regenerating e Cellula V Cells divide to reproduce I. Asexual Reproduction offspring from single parent (daughter cells have identical DNA as parent cell) II. Sexual Reproduction offspring from union of egg and sperm (combine some DNA from both parent cells) Sperm cells and egg cell Budding Hydra Prokaryotes Divide Asexually V Binary Fission “to split in half” V A Chromosome (1 DNA molecule) is duplicated, separates, and then cell divides Binary fission of a bacterium
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Heyer 2 Eukaryotic Cells Have Multiple Chromosomes V Eukaryotic cells have 5–20x more DNA per cell than do bacteria. V Divided into linear dsDNA + chromosomes V If straight, typical chromosome would be ~ 4 cm long. V Humans have 46 different chromosomes – So collectively amounts to ~ 2 m long dsDNA packed into each cell nucleus! (4 m after replication!) Eukaryotic Cells Have Multiple Chromosomes V In division, each new cell needs the correct number and kind of chromosomes –Replicate and divide chromosomes in nucleus –Distribution of organelles Chromosomes Must Duplicate Before Division Human duplicated chromosome Chromosome duplication and separation [Semiconservative Replication] The Cell Cycle V Ordered sequence of events in a cell’s life V Interphase (G 1 /S/G 2 ) : 90% of cell cycle – Most cellular activity V Mitotic phase (M) – Mitosis = nucleus divides – Cytokinesis = membrane divides The eukaryotic cell cycle The Cell Cycle Interphase : 1. G 1 : G rowth stage, part 1 ß Cell is metabolically active and grows larger 2. S: S ynthesis stage ß DNA is replicated 3. G 2 : G rowth stage, part 2 ß growth The eukaryotic cell cycle S Stage All cell reproduction requires DNA duplication V Each cell must have its own copy of genetic material DNA replication in S Stage of Interphase V Then DNA must be separated ( segregation ) so that each cell has a complete copy Mitosis of Mitotic Phase
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Heyer 3
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This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.

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B6A3CellCyclesF09 - Cell Cycles & Life Cycles The DNA...

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