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08 Lecture Ppt


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08 Lecture Ppt

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 8 Cell Division and Reproduction
  2. 2. Cell Division Ensures the Passage of Genetic Information 8-
  3. 3. 8.1 Cell division is involved in both asexual and sexual reproduction <ul><li>Somatic cells - body cells make up most of the organism </li></ul><ul><ul><li>Asexual reproduction - increase in number of somatic cells or the number unicellular organisms </li></ul></ul><ul><li>Germ cells - found only in testes and ovaries, they produce sperm or eggs </li></ul><ul><ul><li>Sexual reproduction – requires the production of eggs and sperm </li></ul></ul>8-
  4. 4. 8.2 Prokaryotes reproduce asexually <ul><li>In bacteria and archaea, reproduction consists of duplicating the single chromosome, located in the nucleoid, and distributing a copy to each daughter cell </li></ul>8-
  5. 5. Figure 8.2 Prokaryotes use binary fission to reproduce 8-
  6. 6. Somatic Cells Have a Cell Cycle and Undergo Mitosis and Cytokinesis 8-
  7. 7. 8.3 The eukaryotic cell cycle is a set series of events <ul><li>Interphase - the time when a cell performs its usual functions </li></ul><ul><li>Figure 8.3A Stages of the cell cycle. </li></ul>8-
  8. 8. M (Mitotic) Stage <ul><li>Cell division occurs during the M stage and encompasses both division of the nucleus and division of the cytoplasm </li></ul><ul><ul><li>Mitosis - nuclear division in the cell cycle </li></ul></ul><ul><ul><li>Cytokinesis - division of the cytoplasm </li></ul></ul>8-
  9. 9. Figure 8.3B Cytokinesis is a noticeable part of the cell cycle 8-
  10. 10. 8.4 Eukaryotic chromosomes are visible during cell division <ul><li>When a eukaryotic cell is not undergoing division, the DNA within a chromosome is a mass of thin threads called chromatin </li></ul><ul><ul><li>Before nuclear division chromatin condenses, </li></ul></ul><ul><ul><li>2 identical chromatids are sister chromatids </li></ul></ul>8-
  11. 11. Figure 8.4A A condensed duplicated chromosome 8-
  12. 12. Somatic Cells Are Diploid (2n) <ul><li>Diploid (2n) - includes two chromosomes of each kind </li></ul><ul><li>During mitosis, a 2n nucleus divides to produce daughter nuclei that are also 2n </li></ul><ul><ul><li>A dividing cell is called the parent cell and the new cells are called the daughter cells </li></ul></ul>8-
  13. 13. Gametes Are Haploid (n) <ul><li>Haploid (n) number of chromosomes, contains only one chromosome of each kind </li></ul><ul><ul><li>Half the diploid number </li></ul></ul><ul><li>Figure 8.4B When sister chromatids separate, each daughter nucleus gets a chromosome </li></ul>8-
  14. 14. 8.5 Mitosis maintains the chromosome number <ul><li>Before mitosis, DNA has replicated, each double helix is in a chromatid and the chromosomes consist of sister chromatids attached at a centromere </li></ul><ul><ul><li>The centrosome - the microtubule-organizing center of the cell divides before mitosis </li></ul></ul><ul><ul><li>Spindle fibers separate the sister chromatids of the duplicated chromosomes </li></ul></ul>8-
  15. 15. 8- Figure 8.5 Phases of mitosis in animal cells and plant cells
  16. 16. Figure 8.5 Phases of mitosis in animal cells and plant cells 8-
  17. 17. 8.6 Cytokinesis divides the cytoplasm <ul><li>Cytokinesis follows mitosis in most cells </li></ul><ul><li>Cytokinesis in plant cells occurs by a process different than in animal cells </li></ul><ul><ul><li>Cell plate - newly formed plasma membrane that expands outward </li></ul></ul>8-
  18. 18. Figure 8.6A Cytokinesis in an animal cell 8-
  19. 19. Figure 8.6B Cytokinesis in plant cells 8-
  20. 20. Cancer Is Uncontrolled Cell Division 8-
  21. 21. 8.7 Cell cycle control occurs at checkpoints <ul><li>The cell cycle has checkpoints that can delay the cell cycle until all is well </li></ul><ul><ul><li>Apoptosis - programmed cell death </li></ul></ul>8-
  22. 22. Figure 8.7 Cell cycle checkpoints 8-
  23. 23. 8.8 Signals affect the cell cycle control system <ul><li>Signaling molecules stimulate or inhibit </li></ul><ul><li>Kinases remove phosphate from ATP and add it to another molecule </li></ul><ul><li>Cyclins combine with kinases </li></ul><ul><li>Control system for cell division control whether kinases and cyclins are present </li></ul>8-
  24. 24. Figure 8.8A Internal signals of the cell cycle are kinases and cyclins 8-
  25. 25. Figure 8.8B A cell-signaling pathway activates the control system to produce kinases and cyclins 8-
  26. 26. Cell Cycle Inhibition <ul><li>Contact Inhibition - In a culture, cells divide until they line a container in a sheet and then stop dividing </li></ul><ul><li>Cells “remember” number of divisions </li></ul><ul><li>Telomere - repeating DNA base sequence </li></ul><ul><ul><li>Each time a cell divides some portion of a telomere is lost </li></ul></ul><ul><ul><li>When telomeres become too short, chromosomes fuse and do not duplicate </li></ul></ul>8-
  27. 27. 8.9 Cancer cells have abnormal characteristics <ul><li>A mutation (a DNA change) causes a cell to divide uncontrollably or ignore apoptosis </li></ul><ul><ul><li>Carcinogenesis - development of cancer </li></ul></ul><ul><li>Characteristics of cancer cells </li></ul><ul><ul><li>Lack differentiation </li></ul></ul><ul><ul><li>Have abnormal nuclei </li></ul></ul><ul><ul><li>Form tumors </li></ul></ul><ul><ul><li>Metastasis - establishing new tumors </li></ul></ul><ul><ul><li>Angiogenesis - formation of new blood vessels </li></ul></ul>8-
  28. 28. Figure 8.9 Development of breast cancer 8-
  29. 29. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 8.10 Protective behaviors and diet help prevent cancer <ul><li>Behaviors that help prevent cancer </li></ul><ul><ul><li>Don’t smoke </li></ul></ul><ul><ul><li>Use sunscreen </li></ul></ul><ul><ul><li>Avoid radiation </li></ul></ul><ul><ul><li>Be tested for cancer </li></ul></ul><ul><ul><li>Be aware of occupational hazards </li></ul></ul><ul><ul><li>Carefully consider hormone therapy </li></ul></ul><ul><li>Dietary guidelines to reduce cancer risk </li></ul><ul><ul><li>Increase consumption of foods rich in vitamins A and C </li></ul></ul><ul><ul><li>Limit consumption of salt-cured, smoked, or nitrite-cured foods </li></ul></ul><ul><ul><li>Include vegetables from the cabbage family </li></ul></ul><ul><ul><li>Be moderate in the consumption of alcohol </li></ul></ul><ul><ul><li>Maintain a healthy weight </li></ul></ul>8-
  30. 30. Meiosis Produces Cells That Become the Gametes in Animals and Spores in Other Organisms 8-
  31. 31. 8.11 Homologous chromosomes separate during meiosis <ul><li>Karyotype - picture of chromosomes in numbered pairs called homologous chromosomes or homologues </li></ul><ul><ul><li>X and Y chromosomes are the sex chromosomes because they contain the genes that determine gender </li></ul></ul><ul><ul><ul><li>Autosomes - all the pairs of chromosomes except the sex chromosomes </li></ul></ul></ul>8-
  32. 32. Figure 8.11 A karyotype shows that the chromosomes occur as pairs 8-
  33. 33. Meiosis <ul><li>Occurs during the production of the sperm and egg </li></ul><ul><li>Requires two divisions </li></ul><ul><ul><li>Meiosis I - the chromosomes of each homologous pair separate </li></ul></ul><ul><ul><li>Meiosis II - the sister chromatids of each duplicated chromosome separate </li></ul></ul>8-
  34. 34. 8-
  35. 35. 8.12 Synapsis and crossing-over occur during meiosis I <ul><li>Synapsis - homologous chromosomes come together and line up side by side forming a tetrad </li></ul><ul><li>Crossing-over - during synapsis, nonsister chromatids exchange genetic material </li></ul>8-
  36. 36. Figure 8.12A Synapsis of homologues 8-
  37. 37. Figure 8.12B Crossing-over of nonsister chromatids 8-
  38. 38. 8.13 Sexual reproduction increases genetic variation <ul><li>Fertilization , the union of a male and a female gamete, enhances genetic variation </li></ul><ul><ul><li>Sexual reproduction brings about genetic variation, and some offspring may have a better chance of survival and reproductive success than others </li></ul></ul>8-
  39. 39. Figure 8.13 Independent assortment increases genetic variation 8-
  40. 40. 8.14 Meiosis requires two division cycles <ul><li>Prophase, metaphase, anaphase, and telophase occur during both meiosis I and meiosis II </li></ul><ul><ul><li>No replication of DNA occurs during a period called interkinesis between meiosis I and II </li></ul></ul>8-
  41. 41. Figure 8.14A Phases of meiosis I 8-
  42. 42. Figure 8.14A Phases of meiosis I 8-
  43. 43. Figure 8.14B Phases of meiosis II 8-
  44. 44. Figure 8.14B Phases of meiosis II 8-
  45. 45. 8.15 The life cycle of most multicellular organisms includes both mitosis and meiosis <ul><li>Life cycle - in sexually reproducing organisms, all the reproductive events from one generation to the next </li></ul><ul><ul><li>Spermatogenesis in males, occurs in the testes and produces sperm </li></ul></ul><ul><ul><li>Oogenesis in females, occurs in the ovaries and produces eggs </li></ul></ul><ul><li>Zygote - product of the sperm and egg joining during fertilization, has homologous pairs of chromosomes </li></ul>8-
  46. 46. Figure 8.15A Life cycle of humans 8-
  47. 47. <ul><li>Figure 8.15B Life cycle of plants Figure 8.15C Life cycle of algae </li></ul>8-
  48. 48. 8.16 Meiosis can be compared to mitosis 8-
  49. 49. Chromosomal Abnormalities Can Be Inherited 8-
  50. 50. 8.17 An abnormal chromosome number is sometimes traceable to nondisjunction <ul><li>Polyploidy - a eukaryote has three or more complete sets of chromosomes </li></ul><ul><li>Aneuploidy - an organism has more or less than the normal number of chromosomes </li></ul><ul><ul><li>Monosomy only one of a type of chromosome </li></ul></ul><ul><ul><li>Trisomy three of a type of chromosome </li></ul></ul><ul><li>Nondisjunction - in meiosis I homologues do not separate and both go into the same daughter cell, or in meiosis II sister chromatids fail to separate and both daughter chromosomes go to the same gamete </li></ul>8-
  51. 51. Figure 8.17A Nondisjunction of chromosomes during meiosis I of oogenesis, followed by fertilization with normal sperm 8-
  52. 52. Figure 8.17B Nondisjunction of chromosomes during meiosis II of oogenesis, followed by fertilization with normal sperm 8-
  53. 53. 8.18 Abnormal chromosome numbers cause syndromes <ul><li>Trisomy 21 (Down Syndrome) </li></ul><ul><ul><li>Over 90% of individuals with Down syndrome have three copies of chromosome 21 </li></ul></ul><ul><li>Abnormal Sex Chromosome Inheritance </li></ul><ul><ul><li>Turner syndrome females are born with only a single X chromosome </li></ul></ul><ul><ul><li>A male with Klinefelter syndrome has two or more X chromosomes in addition to a Y chromosome </li></ul></ul>8-
  54. 54. 8.19 Abnormal chromosome structure also causes syndromes <ul><li>Various agents in the environment, such as radiation, certain organic chemicals, or viruses, can cause chromosomes to break </li></ul><ul><ul><li>Deletion - an end of a chromosome breaks off or two simultaneous breaks lead to the loss of an internal segment </li></ul></ul><ul><ul><li>Duplication - the presence of a particular chromosome segment more than once in the same chromosome </li></ul></ul><ul><ul><li>Inversion - a segment of a chromosome is turned 180 degrees </li></ul></ul><ul><ul><li>Translocation - the movement of a chromosome segment from one chromosome to another nonhomologous chromosome </li></ul></ul>8-
  55. 55. Figure 8.19 Types of chromosomal mutations 8-
  56. 56. Connecting the Concepts: Chapter 8 <ul><li>All cells receive DNA from preexisting cells through the process of cell division </li></ul><ul><ul><li>Mitosis is part of the cell cycle, and there are negative consequences if the cell cycle comes out of synchronization </li></ul></ul><ul><ul><li>Meiosis is part of the production of gametes, which have half the number of chromosomes as the parent cell </li></ul></ul><ul><li>Sexual reproduction increases genetic variability </li></ul>8-