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Cell Reproduction

Cell Reproduction. Prokaryotes Bacteria Eukaryotes Plants & animals. Prokaryotes. Lack a nucleus Have a single chromosome Reproduce asexually by binary fission Include bacteria. Asexual Reproduction contd. Binary fission happens in bacteria, amoeba, some algae

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Cell Reproduction

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  1. Cell Reproduction • Prokaryotes Bacteria • Eukaryotes Plants & animals

  2. Prokaryotes • Lack a nucleus • Have a single chromosome • Reproduce asexually by binary fission • Include bacteria

  3. Asexual Reproduction contd. • Binary fission • happens in bacteria, amoeba, some algae • one parent cell splits into 2 identical daughter cells • Budding • happens in yeast, hydra, corals • parent produces a bud • bud gets detached and develops into offspring which is identical to parent

  4. Steps in Binary Fission • Used by bacteria • Cells increase their cell mass slightly • DNA & cell components are replicated • Each cell divides into 2 daughter cells

  5. Binary Fission of Bacterial Cell

  6. Budding

  7. Eukaryotes • Contain a nucleus & membrane bound organelles • Asexually reproduce cells by mitosis • Also reproduce sexually

  8. Sexual Reproduction in Animals • involves specialized sex cells called gametes (haploid Cells) • the union of a male and female gamete results in the formation of a zygote that develops into a new individual

  9. Cell Cycle • Stages in growth & division • G0 Resting Phase • G1 Phase • S Phase • G2 Phase • M Phase • Cytokinesis

  10. G0 Phase • After Cell Division • Cell At Rest • From here some cells will remain in the G0 Phase and others will go into G1.

  11. G1 Phase • First growth stage • Cell increases in size • Cell prepares to copy its DNA

  12. Synthesis Phase • Copying of all of DNA’s instructions • Chromosomes duplicated

  13. G2 Phase • Time between DNA synthesis & mitosis • Cell continues growing • Needed proteins produced

  14. Mitosis Phase • Cell growth & protein production stop • Cell’s energy used to make 2 daughter cells (Diploid Cells) • Called mitosis or karyokinesis (nuclear division)

  15. Life Cycle of a Cell Mitosis is a cycle with no beginning or end.

  16. Interphase – Resting Stage • Cells carrying on normal activities • Chromosomes aren’t visible • Cell metabolism is occurring • Occurs before mitosis

  17. Interphase

  18. Stages of Mitosis • Prophase • Metaphase • Anaphase • Telophase

  19. Cells Undergoing Mitosis

  20. Steps in Prophase • DNA coils tightly & becomes visible as chromosomes • Nuclear membrane disappears • Nucleolus disappears • Centrioles migrate to poles • Spindle begins to form

  21. Prophase

  22. Eukaryotic Chromosome

  23. Human Chromosomes

  24. Steps in Metaphase • Spindle fibers from centrioles attach to each chromosome • Cell preparing to separate its chromosomes • Cell aligns its chromosomes in the middle of the cell

  25. Metaphase

  26. Steps in Anaphase • Cell chromosomes are separated • Spindle fibers shorten so chromosomes pulled to ends of cell

  27. Mitotic Spindle

  28. Anaphase

  29. Steps in Telophase • Separation of chromosomes completed • Cell Plate forms (plants) • Cleavage furrow forms(animals) • Nucleus & nucleolus reform • Chromosomes uncoil

  30. Telophase Plant Animal

  31. Cytokinesis • Occurs after chromosomes separate • Forms two, identical daughter cells

  32. Cytokinesis Cell Plate Forming in Plant Cells

  33. Cell that do not go through Mitosis • Muscle Cell-Why? Fused fibers preventing cell division • Some Neuron Cells –Why? Have lost there centrioles and can no longer reproduce. • Blood Cells-Why? Mature and No longer have a nucleus • Sex Cells: They go through meiosis. • Most of the cells never leave the G0 phase.

  34. Cancer • Cancer is a disease of uncontrolled cell division. It starts with a single cell that loses its control mechanisms due to a genetic mutation. That cell starts dividing without limit, and eventually kills the host. • Normal cells are controlled by several factors. • Normal cells stay in the G1 stage of the cell cycle until they are given a specific signal to enter the S phase, in which the DNA replicates and the cell prepares for division. Cancer cells enter the S phase without waiting for a signal. • Normal cells are mortal. This means that they can divide about 50 times and then they lose the ability to divide, and eventually die. This “clock” gets re-set during the formation of the gametes. Cancer cells escape this process of mortality: they are immortal and can divide endlessly.

  35. THE END

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