Cell division 09

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Cell division 09

  1. 1. Mitosis and Meiosis Cell Division:
  2. 2. Objectives:  To distinguish between chromatin and chromosome  To define homologous chromosomes  To distinguish between diploid and haploid
  3. 3. Chromatin found in the nucleus of a nondividing cell  made of DNA and protein
  4. 4. DNA in chromatin replicates before cell division Chromatin becomes highly coiled and condensed Becomes visible as a chromosome
  5. 5. A Chromosome consists of 2 identical chromatids Centromere – point at which each pair of chromatids is attached centromere
  6. 6. Homologous Chromosomes pair of chromosomes that have same size and shape  found in sexually reproducing organisms  human body cells have 23 homologous pairs
  7. 7. Diploid (2N) – cell that contains both chromosomes of a homologous pair human body cells 46
  8. 8. Haploid # (N) – cell that has only one chromosome of each homologous pair egg & sperm human sex cells 23
  9. 9. Objectives:  To describe the cell cycle  To define mitosis  To list and describe the stages of mitosis
  10. 10. Cell Cycle – period from beginning of one mitosis to beginning of next Cell cycle consists of three stages: I. Interphase II. Mitosis III. Cytokinesis
  11. 11. Interphase cell growth and development DNA replication
  12. 12. Interphase Plant cell Animal cell
  13. 13. Mitosis – division of the cell nucleus  number of chromosomes remains the same  occurs in body cells and unicellular organisms  produces identical daughter cells
  14. 14. Mitosis in Human Body Cells 46 (2N) 46 (2N) 46 (2N)
  15. 15. Stages of Mitosis P M A T r o p h a s e e t a p h a s e e l o p h a s e n a p h a s e
  16. 16. 1) Prophase  chromosomes become visible  nuclear membrane disappears  centrioles move to opposite ends of cell and form the spindle
  17. 17. 2) Metaphase  chromosomes line up along the equator of the cell
  18. 18. 3) Anaphase  chromatids separate and are pulled to opposite ends of the cell
  19. 19. 4) Telophase  chromosomes become threadlike forming chromatin  nucleus forms in each cell
  20. 20. Plant cell mitosis Animal cell mitosis
  21. 21. Cytokinesis - division of the cytoplasm
  22. 22. Objectives:  To define meiosis  To list and describe the stages of meiosis
  23. 23. Meiosis – division of the nucleus that reduces the number of chromosomes by half  involved in sexual reproduction  produces sex cells
  24. 24. Overview of Meiosis 46 (2N) 23 (N) 23 (N) 23 (N) 23 (N) 23 (N) 23 (N) Meiosis I (PMAT I) Meiosis II (PMAT II)
  25. 25. Meiosis I Prophase I • homologous chromosomes pair up during synapsis forming tetrads • spindle appears • crossing over may occur
  26. 26. tetrad tetrad
  27. 27. Crossing Over Between Homologous Chromosomes
  28. 28. Metaphase I  homologous pairs of chromosomes line up along the equator of the cell
  29. 29. Anaphase I  homologous pairs of chromosomes separate
  30. 30. Telophase I  cytoplasm divides forming 2 new daughter cells
  31. 31. Meiosis II  similar to the stages of mitosis  chromosomes line up in the center of each cell  chromatids separate  4 cells are produced
  32. 32. Prophase II
  33. 33. Metaphase II
  34. 34. Anaphase II
  35. 35. Telophase II
  36. 36. Products of Meiosis
  37. 37. Objectives:  To define gametes  To define zygote  To define genetic recombination
  38. 38. Gametes sex cells (sperm and egg) human sperm cells human egg cell
  39. 39. cell that results from the fusion of gametes  forms when sperm fertilizes the egg Zygote
  40. 40. process that results in genes being combined in new ways during meiosis  introduces variation between parents and offspring  gives survival advantage to sexually reproducing organisms Genetic Recombination
  41. 41. Objectives:  To define cancer  To describe the role of gene expression in cancer  To describe the causes of cancer
  42. 42. abnormal, uncontrolled growth of cells that can spread from one part of the body to another Cancer
  43. 43. Tumor – abnormal proliferation of cells that results from uncontrolled, abnormal cell division Types of Tumors benign – cells remain within a mass and do not spread malignant – cells may invade and destroy healthy tissues elsewhere in the body
  44. 44. spread of cancer cells beyond the original site of growth cells grow as malignant tumor in epithelium Metastasis
  45. 45. Types of Genes Implicated in Cancer Development 1. Oncogenes 2. Tumor-Suppressor Genes 3. DNA Repair Genes
  46. 46. proto-oncogene – a gene which regulates normal cell growth Oncogene – mutated proto- oncogene that can cause uncontrolled cell growth and proliferation
  47. 47. inhibits cell division and prevents tumor formation Tumor-Suppressor Gene mutations in tumor suppressor genes promote cell division and allow genetically damaged cells to grow out of control
  48. 48. repairs mutations in cellular DNA before a cell enters mitosis • mutations in repair genes leads to continued transcription of mutated DNA sequences and affects normal cell functioning DNA Repair Gene
  49. 49. Breast Cancer Cell Line Karyotype
  50. 50. any substance that can induce or promote cancer Carcinogen

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