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The Cellular Basis of Inheritance: Mitosis, Meiosis, and Cancer

Explore how cells divide through mitosis and meiosis, leading to growth and reproduction. Learn about the cell cycle, mitotic stages, cancer development, and treatment options.

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The Cellular Basis of Inheritance: Mitosis, Meiosis, and Cancer

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  1. Chapter 9 – The Cellular Basis of Inheritance College Prep Biology Mr. Martino

  2. 9.1 All cells come from cells. • Repair and Growth • The outer layer of skin is dead, new living cells underneath replace the dead layer that rubs off. • Growth from infant to adult results in trillions of cell divisions. • Reproduction • Asexual reproduction = one cell splits into two new cells (bacteria); genetic clone • Sexual reproduction = two parents contribute to the offspring (sperm and egg); increases genetic variation

  3. 9.2 Dividing Cells - Overview • Before cells can reproduce – they must undergo nuclear division • Mitosis: the division of regular body (somatic) cells • Meiosis: the division of cells that form sex (gamete) cells or germ cells • Chromosome: a DNA molecule and its proteins • Chromatin: long, thin threads of DNA and protein that eventually coils to become chromosomes as the cell gets ready to divide • Centromere: region that joins the sister chromatids

  4. Chromosome # varies depending upon organism • Ex. Humans have 46 chromo. in each somatic (body) cell • Diploid: (2n) cells have a pair of each chromosome – somatic cells • Haploid: (n) cell with only 1 of each chromosome – gamete (sex) cells

  5. 9.2 Cell Cycle • Cell division replaces old, worn out cells, or damaged cells • Millions of cells divide every second in humans (nerve and muscles do not) • Cell cycle: sequence of events from when daughters cells are formed until they form new ones • Interphase: 90% of cell cycle – chromo. duplicate & cell grows • G1 – growth • S – DNA replication • G2 – growth & checking of chromo.

  6. Division of most cells involves 2 processes that make op the M phase: • 1. Mitosis: nucleus and chromo. divide • Chromo. are clearly visible • 2. Cytokinesis: cytoplasm divides • Mitosis is unique to eukaryotes and very accurate

  7. 9.3 Mitosis - Overview • Mitosis is a continuous process, but consists of 4 main stages: • 1. Prophase • 2. Metaphase • 3. Anaphase • 4. Telophase • Spindle apparatus: special microtublues that move chromosomes

  8. Interphase • Interphase: period of growth when the cell synthesizes new molecules and organelles • By G2, most of contents has been doubled • Chromatin has been doubled • At least 1 nucleolus is visible

  9. Prophase • Chromatin fibers become more tightly coiled and folded – becoming chromosomes • Sister chromatids are joined at centromeres • Nucleoli disappear • Nuclear envelope disappears • Microtubules attach to chromosomes • Sisters are starting to move

  10. Metaphase • Mitotic spindle is fully formed • Chromosomes aligned at metaphase plate with centromeres on plate

  11. Anaphase • Begins when two sisters come apart – becoming chromosomes • ATP powers the pull of the chromosomes (centromeres first) toward opposite poles • Spindles not attached to chromosomes lengthen – elongating the cell • Ends when chromosomes reach poles

  12. Telophase and Cytokenesis • Reverse of prophase • Cell elongation continues • Nuclei appear at poles • Chromosomes uncoil becoming chromatin • Nucleoli reappear • Mitotic spindle disappears • 2 identical daughter nuclei have formed • Cytokinesis follows forming 2 identical cells

  13. Animal Cell Mitosis

  14. Plant Cell Mitosis

  15. Division of Animal Cell Cytoplasm • Cytokinesis typically occurs in telophase, although it can begin in late anaphase • In animals, it is referred to as cleavage • Cleavage furrow: shallow groove on cell surface which is the first sign of cleavage • A ring of microfilaments acts like drawstrings and gradually pinches the cell in two

  16. Division of Plant Cell Cytoplasm • Vesicles collect at center of cell and eventually fuse to form the cell plate • Cell plate grows outwards until it fuses with the cell membrane

  17. Cell Division Video’s • Bacteria Animation • Embryogenesis • Neuron Division • Plant and Animal Cell Division Movies

  18. 9.4 Cancer cell grow and divide out of control • Tumors and Cancer • Benign tumor – abnormal mass of normal cells • Sometimes cause health problems but can usually be removed by surgery • Malignant tumor – masses of cells that result from reproduction of cancer cells • Cancer – disease caused by severe disruption of the cell cycle which may result in death • Metastasis – the spread of cancer cells from their original point

  19. Cancer Treatment • Malignant tumors can be removed by surgery, difficult to remove all of the tumor. • Radiation treatment exposes the tumor to high levels of radiation (light or ionizing waves) that destroy the abnormal cells. • Side effects: damage to ovaries and testes • Chemotherapy treats the tumor with drugs that interfere with the spindle apparatus of the cancerous cells disrupting division • Side effects: damage to hair follicles and nausea.

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