PPP-Ch.2_ b - CHAPTER 2 Mitosis and Meiosis Dr. Sanghamitra...

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Unformatted text preview: CHAPTER 2 Mitosis and Meiosis Dr. Sanghamitra Mohanty Main areas of discussion: Cell structure Mitosis Meiosis Spermatogenesis and oogenesis Electron microscopy of mitotic and meiotic chromosomes In eukaryotes, transmission of genetic material from one generation of cells to the next involves mitosis and meiosis. Meiosis leads to production of gametes with half the number of chromosomes as the parent cell. Mitosis leads to production of two cells, each with the same number of chromosomes as the parent cell. In eukaryotes, DNA resides in the nucleus and organelles reside in the cytoplasm (Figure 2.1). Figure 2.1 A generalized animal cell The cell is surrounded by a plasma membrane. Plant and bacterial cells also have a cell wall composed mainly of cellulose and peptidoglycan, respectively . . DNA in the nucleus is complexed with an array of acidic and basic proteins into thin fibers. During nondivisional phases of the cell cycle, these fibers are uncoiled and dispersed into chromatin. Chromatin fibers coil and condense to form chromosomes during mitosis and meiosis. Centrioles in the cytoplasm are located in a specialized region called the centrosome. Centrioles organize spindle fibers for movement of chromosomes during meiosis and mitosis. Parts of a chromosome: Figure 2.3 Chromosomes Exist in Homologous Pairs in Diploid Organisms: In each homologous pair of chromosomes, one member is derived from each parent. Sex-determining chromosomes are usually not homologous (Figure 2.4) yet behave as homologs in meiosis. Figure 2.4 Homologous pair of chromosomes in a human cell Mitosis Partitions Chromosomes into Dividing Cells: Genetic material is partitioned to daughter cells during nuclear division (karyokinesis). Cytoplasmic division (cytokinesis) follows . . The cell cycle is composed of interphase and mitosis. Interphase includes: S phase, during which DNA is synthesized Two gap phases (G1 and G2) G0 is a point in the G1 phase where cells withdraw from the cell cycle and enter a nondividing but metabolically active state. Mitosis has discrete stages: prophase prometaphase metaphase anaphase telophase Mitosis produces daughter cells with a full diploid complement of chromosomes.diploid complement of chromosomes....
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PPP-Ch.2_ b - CHAPTER 2 Mitosis and Meiosis Dr. Sanghamitra...

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