Biology Chapter 12 Objectives

Biology Chapter 12 Objectives - Chapter 12 The Cell Cycle...

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Chapter 12 The Cell Cycle The Key Roles of Cell Division 1. Cell division divides and forms duplicate offspring; the division of one cell reproduces an entire organism. Cell division can produce progeny from some multicellular organisms and also enables sexually reproducing organisms to develop from a single cell. 2. A prokaryotic genome is a single long DNA molecule. Eukaryotic genomes usually consist of a number of DNA molecules. 3. There are major events of cell division that enable the genome of one cell to be passed on to two daughter cells. This is mitosis, the division of the nucleus, which is then followed by cytokinesis, the division of the cytoplasm. 4. Chromosome number changes throughout the human life cycle. First, 46 chromosomes are inherited, one set of 23 from each parent. In gametes, the number of chromosomes are reduced from 26 to 23, while fertilization fuses two gametes together and returns the chromosome number back to 46. The Mitotic Cell Cycle 5. The phases of the cycle are the mitotic (M) phase and interphase, which can be divided into subphases, the G 1 phase, the S phase, and the G 2 phase. The M phase includes both mitosis and cytokinesis and is usually the shortest part of the cell cycle. Interphase is when the cell grows and copies its chromosomes in preparation for cell division. 6. The phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase. During prophase, the chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope. The nucleoli disappear, and each duplicated chromosome appears as two identical sister chromatids joined together. The mitotic spindle beings to form, and the centrosomes move away from each other. During prometaphase, the nuclear envelope fragments. The microtubules extend from each centrosome toward the middle of the cell. Each of the two chromatids of a chromosome now has a
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