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Chapter 9 – The Cellular Basis of Inheritance

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

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Chapter 9 – The Cellular Basis of Inheritance

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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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