BIOLOGY FORM 4 CHAPTER 5 PART 1 - MITOSIS

  1. 1. BIOLOGY FORM 4 CHAPTER 5 PART 1 CELL DIVISION - MITOSIS
  2. 2. CHROMOSOMES: • carry the genetic code • contain all characters of cells Chromosomes Composed of chromatin – a complex of DNA and proteins
  3. 3. DNA is packed The coiling and condensing of DNA
  4. 4. The total extended length of DNA in a human cell is nearly 2m, but this must be fit into a nucleus with a diameter of only 5 to 10μm.
  5. 5. Number of Chromosomes Ant: 2 Fruit Flies: 8 Carrots: 20 Shrimp: 254 Turkey: 82 Dog: 48 Adders tongue (Fern): 1260 Largest number of chromosomes
  6. 6. The human genome (the total number of chromosomes) in humans is: 23 homologous chromosomal pairs Set 23: Sex chromosomes Set 23: Sex chromosomes
  7. 7. HHoommoollooggoouuss cchhrroommoossoommeess  Paired chromosomes - From maternal & paternal sources - control same inherited characters - homologous = same information
  8. 8. Why are chromosomes drawn in a different colour? Chromosomes are of either MATERNAL or PATERNAL origin. from Mum from Dad
  9. 9. KKeeeeppiinngg CCeellllss IIddeennttiiccaall TThhee iinnssttrruuccttiioonnss ffoorr mmaakkiinngg cceellll ppaarrttss aarree eennccooddeedd iinn tthhee DDNNAA,, ssoo eeaacchh nneeww cceellll mmuusstt ggeett aa ccoommpplleettee sseett ooff tthhee DDNNAA mmoolleeccuulleess
  10. 10. DDNNAA RReepplliiccaattiioonn DDNNAA mmuusstt bbee ccooppiieedd oorr rreepplliiccaatteedd bbeeffoorree cceellll ddiivviissiioonn EEaacchh nneeww cceellll wwiillll tthheenn hhaavvee aann iiddeennttiiccaall ccooppyy ooff tthhee DDNNAA OOrriiggiinnaall DDNNAA ssttrraanndd TTwwoo nneeww,, iiddeennttiiccaall DDNNAA ssttrraannddss
  11. 11. IIddeennttiiccaall DDaauugghhtteerr CCeellllss PPaarreenntt CCeellll TTwwoo iiddeennttiiccaall ddaauugghhtteerr cceellllss
  12. 12. CELL CYCLE - preparation for cell division
  13. 13. Three Main stages in the Cell Cycle 3. Interphase (growth - 90% of the time) 2. Cytokinesis (Cytoplasm division) 1. Mitosis (nuclear division)
  14. 14. Interphase has three subphases: 3. G2 (Gap 2) 2. S phase (DNA synthesis) 1. G1 (Gap 1)
  15. 15. What happens in each subphase? synthesis and replication of organelles synthesis of proteins and RNA DDNNAA ssyynntthheessiiss cells that do not divide again enter G0
  16. 16. Three organelles replicate: Mitochondria Chloroplasts Centrioles
  17. 17. The length of the Cell Cycle depends on: The type of cell:  usually the more specialised the cell the less likely it is to divide External factors e.g.: temperature food oxygen supplies RBC are replaced at a rate of 2-3 million/sec Nerve cells usually never divide
  18. 18. © 2003 John Wiley and Sons Publishers
  19. 19. 21 SSkkeettcchh tthhee CCeellll CCyyccllee DDaauugghhtteerr CCeellllss DDNNAA CCooppiieedd CCeellllss MMaattuurree CCeellllss pprreeppaarree ffoorr DDiivviissiioonn CCeellll DDiivviiddeess iinnttoo IIddeennttiiccaall cceellllss
  20. 20. Question: Suggest explanations for the following observation. Interphase is not a static stage of the cell cycle. (2) Proteins and RNA are synthesised, DNA is replicated and organelles are synthesised or replicated.
  21. 21. Question : This question is concerned with cell division. Give a brief description of the Cell Cycle. (2) Nuclear division is followed by cytokinesis which results in two cells. Each cell enters interphase where proteins and RNA are synthesized during the G1 phase. DNA replicates during the S phase and organelles are synthesized or replicated during the G2 phase.
  22. 22. Question: The graph below illustrates how the quantity of DNA, within a mammalian somatic cell, varies during different phases of the cell’s cycle. Additionally the graph shows the two growth phases, G1 and G2, which are separated by an intermediate phase S. a) In terms of the graph above, explain what is happening within the cell during phase S. (2)
  23. 23. DNA replicates. Each chromosome consists of two sister chromatids. b)State ONE process other than cell growth which occurs during phase G2. (1) Organelles are synthesised or they replicate.
  24. 24. Cells divide for three reasons: 1.For growth e.g. formation of a bud in Hydra 2. To produce gametes or spores 3.To replace damaged cells Mucor Salmon gametes mixing
  25. 25. TWO types of cells in the body Non-reproductive or somatic cells Non-reproductive or somatic cells Gametes & Spores Gametes & Spores diploid number of chromosomes (2n) phagocyte neurones haploid number (n) spermatozoa pollen grains (microspores)
  26. 26. Life cycle of animals Human Human Haploid(n) – 23 chromosomes Haploid(n) – 23 chromosomes Diploid Diploid ((22nn)) – – 4 466 c chhrroommoossoommeess
  27. 27. types of nuclear division
  28. 28. - the process by which a cell nucleus divides to produce two daughter nuclei containing identical sets of chromosomes to the parent cell Mitosis in root tip
  29. 29. - the process by which a cell nucleus divides to produce four daughter nuclei each containing half the number of chromosomes of the original nucleus - also called reduction division Meiosis forms the ovum and spermatozoa in animals.
  30. 30. MITOSIS
  31. 31. SSiiggnniiffiiccaannccee ooff mmiittoossiiss 3. Regeneration and cell replacement 1. Growth 2. Replace dead & damaged cells
  32. 32. Binary fission in Amoeba Budding in Yeast 4. Asexual reproduction  Single-celled eukaryotes reproduce asexually  Simple multicellular eukaryotes reproduce asexually Hydra by budding
  33. 33. Mitosis occurs in Animals Animals In Non-reproductive or somatic cells In Non-reproductive or somatic cells All cells in the body except reproductive cells phagocyte Plants •In meristem cells •Tip of root /shoot
  34. 34. Centromeres, centrioles and centrosomes Centromere is a point of constriction on the chromosome
  35. 35. Centrioles organelles in the cytoplasm only found in animals cells absent in higher plants occur in pairs lie at right angles to each other able to self replicate Mitotic centre (centrosome) Mitotic centre (centrosome) Centriole
  36. 36. Centrosomes  are organelles located near the nucleus  are not membrane-bound and serve as a mitotic centre in animals – absent in plants  divide and migrate to opposite poles of the cell during mitosis
  37. 37. Centrosomes  centrosomes and NOT centrioles are responsible to assemble the spindle fibres Spindle fibres  formed during mitosis and meiosis  it arranges the chromosomes into their correct positions in preparation for cell division. Spindle fibres
  38. 38. The spindle serves as a: 1. ‘railroad track’ along which the chromosomes will move 2. framework keeping the two poles apart
  39. 39. NNOO The spindle fibres originate from other mitotic centres
  40. 40. Interphase: A stage prior to mitosis Animal Cell Plant Cell
  41. 41. Interphase – prior to mitosis each chromosome now exists as a pair of chromatids joined together by a centromere
  42. 42. Interphase – prior to mitosis at this stage each cell is 4n (four copies of each DNA molecule, two in each chromosome of a homologous pair) A homologous pair Four copies of each DNA molecule
  43. 43. Interphase – prior to mitosis Chromosomes:  are long & thin  dispersed in nucleus  cannot be seen individually Centrioles have replicated Diffused chromosomes
  44. 44. MITOSIS
  45. 45. G1 S telophase anaphase metaphase prophase Mitosis G2 interphase Stages of mitosis in the cell cycle
  46. 46. FFoouurr MMiittoottiicc SSttaaggeess PPrroopphhaassee MMeettaapphhaassee AAnnaapphhaassee TTeelloopphhaassee
  47. 47. Parent cell Chromosomes are copied and double in number Chromosomes now split 2 daughter cells identical to original
  48. 48. 52 MMiittoottiicc SSttaaggeess
  49. 49. PROPHASE usually the longest phase of division the chromosomes shorten and thicken by coiling: condensation individual chromosomes can be seen
  50. 50. LLaattee PPrroopphhaassee NNuucclleeuuss && NNuucclleeoolluuss hhaavvee ddiissiinntteeggrraatteedd CChhrroommoossoommeess
  51. 51. PROPHASE in animal cells:  the centrioles move to opposite poles of the cell  asters form Asters: short microtubules radiating from the centrioles Function of asters: help to manipulate chromosomes during nuclear division to ensure that each daughter cell has the appropriate complement of chromosomes
  52. 52. PROPHASE  the nucleolus disappear the nuclear membrane breaks up spindle fibre is formed
  53. 53. PROPHASE Animal Cell Plant Cell Spindle fibers
  54. 54. What is 2n for this cell? 2n = 8
  55. 55. RReevviieeww ooff PPrroopphhaassee WWhhaatt tthhee cceellll llooookkss lliikkee WWhhaatt’’ss hhaappppeenniinngg
  56. 56. imaginary plane through the center of the cell where the chromosomes align
  57. 57. METAPHASE Chromosomes line up around the equator of the spindle, attached by their centromeres to the spindle fibres. AAnniimmaall CCeellll PPllaanntt CCeellll
  58. 58. 70 MMeettaapphhaassee CChhrroommoossoommeess lliinneedd aatt tthhee EEqquuaattoorr AAsstteerrss aatt tthhee ppoolleess SSppiinnddllee FFiibbeerrss
  59. 59. 71 MMeettaapphhaassee AAsstteerr CChhrroommoossoommeess aatt EEqquuaattoorr
  60. 60. ANAPHASE  this stage is very rapid  the centromeres split into two
  61. 61. ANAPHASE  the spindle fibres pull the daughter centromeres to opposite poles  the separated chromatids are pulled behind the centromeres
  62. 62. Why are the chromosomes ‘V’ shaped? As the chromosome is pulled towards the pole at the centromere.
  63. 63. Chromatid attachment and separation
  64. 64. ANAPHASE Animal Cell Plant Cell
  65. 65. AAnnaapphhaassee SSiisstteerr CChhrroommaattiiddss bbeeiinngg sseeppaarraatteedd
  66. 66. AAnnaapphhaassee RReevviieeww WWhhaatt tthhee cceellll llooookkss lliikkee WWhhaatt’’ss ooccccuurrrriinngg
  67. 67. TELOPHASE  the chromosomes:  reach the poles of the cell  uncoil and lengthen  spindle fibres disintegrate  nuclear envelope re-forms  nucleoli reappear  mitosis is complete at the end of telophase
  68. 68. TELOPHASE can be viewed as a reversal of prophase, bringing the cell back to the state of interphase Animal Cell Plant Cell
  69. 69. CCoommppaarriissoonn ooff AAnnaapphhaassee && TTeelloopphhaassee 82
  70. 70. IIddeennttiiccaall DDaauugghhtteerr CCeellllss CChhrroommoossoommee nnuummbbeerr tthhee ssaammee,, bbuutt cceellllss ssmmaalllleerr tthhaann ppaarreenntt cceellll WWhhaatt iiss tthhee 22nn oorr ddiippllooiidd nnuummbbeerr?? 22
  71. 71. RReevviieeww ooff MMiittoossiiss PPrroopphhaassee MMeettaapphhaassee AAnnaapphhaassee TTeelloopphhaassee CCyyttookkiinneessiiss
  72. 72. Fig. 12.5 left Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  73. 73. Fig. 12.5 right Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  74. 74. AAmmoouunntt ooff DDNNAA dduurriinngg cceellll ccyyccllee
  75. 75. Cell division is still not complete at the end of mitosis: as the division of the cytoplasm has not yet begun cytokinesis: the division of the cytoplasm cytokinesis normally:  follows telophase  leads into the G1 phase of interphase
  76. 76. Cytokinesis occurs differently in animal and plant cells
  77. 77. Cytokinesis in animal cells Microfilaments draw in the cell surface membrane to form a cleavage furrow
  78. 78. Cytokinesis in animal cells
  79. 79. Cytokinesis in plant cells Cell Plate Forming in Plant Cells
  80. 80. Cytokinesis: Plant Cells Cell Plate Formation Vesicles from the Golgi apparatus appear at the equatorial plate. Contents of vesicles form the cell plate – the beginning of the new cell wall. These fuse to form new plasma membrane.
  81. 81. Cytokinesis in plant cells
  82. 82. Mitosis: plant vs animal cells Plant cell Animal Cell Centrioles, Centrosomes & Aster Absent Present Cytokinesis Cell plate formation Cleavage furrow
  83. 83. Mitosis – Bone Cell Slides 1 2 Parent cell Chromosomes copied 3 4 5 Cells split Copies separating 2 daughter cells
  84. 84. Interphase & Mitosis in Plant cells Interphase Early Prophase Late Prophase Metaphase Early Anaphase Telophase Late Anaphase Daughter cells
  85. 85. MMiittoossiiss AAnniimmaattiioonn NNaammee eeaacchh ssttaaggee aass yyoouu sseeee iitt ooccccuurr??
  86. 86. IInntteerrpphhaassee PPrroopphhaassee MMeettaapphhaassee TTeelloopphhaassee AAnnaapphhaassee NNaammee tthhee MMiittoottiicc SSttaaggeess:: NNaammee tthhiiss?? NNaammee tthhiiss??
  87. 87. Question: A researcher is provided with onion bulbs which are sprouting following dormancy. She intends to use these bulbs to study mitosis in onion cells. Which parts of the bulb are suitable for this purpose? 2-3 mm from the root tips
  88. 88. Q: Account for the changes in the quantity of DNA in the cell during mitosis. (2) At the end of mitosis, quantity of DNA returns to the original value as sister chromatids separate. M G1 S G2
  89. 89. Question: The drawing shows a stage of mitosis in an animal cell. a)Name this stage of mitosis. Anaphase b) Describe and explain what happens during this stage which ensures that two genetically identical cells are produced. The centromere splits and the sister chromatids carrying the same genetic information move to opposite poles.
  90. 90. The table shows the average duration of each stage of the cell cycle in the cells of a mammalian embryo. Give one piece of evidence from the table which indicates that these cells are multiplying rapidly. Stage Mean duration / minutes Interphase 12 Prophase 50 Metaphase 15 Anaphase 10 Telophase 42 Interphase is short.
  91. 91. Question : A student examined the cells in the garlic root tip under the microscope, and obtained the following data. What do you conclude? Stage Number of cells Prophase 74 Metaphase 18 Anaphase 8 Telophase 10 Prophase is the LONGEST phase and anaphase the SHORTEST.
  92. 92. Question: A scientist intends to observe mitosis in cells of the common onion (Allium cepa). 1. Which part of the onion plant should the scientist use for observing cells undergoing mitosis? (1) Root tip. 2. Why is this part of the plant particularly suitable for this purpose? (2) The root tip is a growing point in plants. It contains a meristematic region where cells are continuously dividing.
  93. 93. 3.Describe how the scientist would process the specimen (the plant structure referred to in Question 1) in order to be able to observe mitosis through a light microscope. Your answer should refer the steps required to prepare the specimen, to the staining procedure and to the temporary mounting of the specimen on a microscope slide. (9)
  94. 94. The tips have been stained red with Feulgen stain. AAcceettiicc oorrcceeiinn ssttaaiinn ccaann bbee uusseedd ttoooo..
  95. 95. MMiittoossiiss iinn OOnniioonn RRoooott TTiippss DDoo yyoouu sseeee aannyy ssttaaggeess ooff mmiittoossiiss??
  96. 96. 113 IIddeennttiiffyy tthhee SSttaaggeess EEaarrllyy,, MMiiddddllee,, & LLaattee PPrroopphhaassee LLaattee PPrroopphhaassee Metaphase AAnnaapphhaassee LLaattee AAnnaapphhaassee TTeelloopphhaassee TTeelloopphhaassee & CCyyttookkiinneessiiss ?? ?? ?? ?? ?? ?? ??
  97. 97. 114 LLooccaattee tthhee FFoouurr MMiittoottiicc SSttaaggeess iinn PPllaannttss MMeettaapphhaassee PPrroopphhaassee AAnnaapphhaassee TTeelloopphhaassee
  98. 98. QQuueessttiioonn:: 4. The scientist draws some of the cells that have been observed. In which stage of the cell cycle are the cells shown below? (4) Cell A: metaphase Cell B: interphase Cell C: anaphase Cell D: prophase
  99. 99. 10. In humans, each cell (except sex cells) has how many chromosomes? ______ 11. After mitosis, how many daughter cells are produced? _______ 12. After mitosis (in a human cell), each daughter cell has how many chromosomes? _____ 13. How many phases are in MITOSIS? ___________ 14. Which phase of the cell cycle is the longest? _________ 15. During which phase does cytokinesis begin? __________
  100. 100. Uncontrolled Mitosis Cell ddiivviissiioonn iiss nnoorrmmaallllyy ccoonnttrroolllleedd IIff mmiittoossiiss iiss nnoott ccoonnttrroolllleedd,, uunnlliimmiitteedd cceellll ddiivviissiioonn ooccccuurrss ccaauussiinngg ccaanncceerroouuss ttuummoorrss.. CCaanncceerr cceellllss CCaanncceerr == ggeenneettiicc ddiisseeaassee ccaauusseedd bbyy uunnccoonnttrroolllleedd mmiittoossiiss CCaanncceerr == ggeenneettiicc ddiisseeaassee ccaauusseedd bbyy uunnccoonnttrroolllleedd mmiittoossiiss dduuee ttoo sseevveerree ddiissrruuppttiioonn iinn tthhee mmeecchhaanniissmm tthhaatt ccoonnttrroollss cceellll ccyyccllee dduuee ttoo sseevveerree ddiissrruuppttiioonn iinn tthhee mmeecchhaanniissmm tthhaatt ccoonnttrroollss cceellll ccyyccllee
  101. 101. • IIff tthhee aabbnnoorrmmaall cceellllss rreemmaaiinn aatt tthhee oorriiggiinnaattiinngg ssiittee,, tthhee lluummpp iiss ccaalllleedd aa bbeenniiggnn ttuummoorr.. • ccaann bbee rreemmoovveedd bbyy ssuurrggeerryy.. • IIff tthhee aabbnnoorrmmaall cceellllss rreemmaaiinn aatt tthhee oorriiggiinnaattiinngg ssiittee,, tthhee lluummpp iiss ccaalllleedd aa bbeenniiggnn ttuummoorr.. • ccaann bbee rreemmoovveedd bbyy ssuurrggeerryy.. • IInn aa mmaalliiggnnaanntt ttuummoorr,, tthhee cceellllss lleeaavvee tthhee oorriiggiinnaall ssiittee.. • aarree ccaarrrriieedd bbyy tthhee bblloooodd aanndd llyymmpphh ssyysstteemm ttoo ootthheerr ttiissssuueess,, aanndd ssttaarrtt mmoorree ttuummoorrss.. • IInn aa mmaalliiggnnaanntt ttuummoorr,, tthhee cceellllss lleeaavvee tthhee oorriiggiinnaall ssiittee.. • aarree ccaarrrriieedd bbyy tthhee bblloooodd aanndd llyymmpphh ssyysstteemm ttoo ootthheerr ttiissssuueess,, aanndd ssttaarrtt mmoorree ttuummoorrss..
  102. 102. APPLICATION OF KNOWLEDGE ON MITOSIS IN CLONING
  103. 103. Cloning Dolly 1997 - 2003 (Roslin Institute http://www.roslin.ac.uk/library/) BBoorrnn iinn SSccoottllaanndd, DDoollllyy wwaass tthhee ffiirrsstt mmaammmmaall ttoo bbee cclloonneedd ((119977)) TThhiiss sshhoowweedd tthhaatt DDNNAA iinn aadduulltt cceellllss ccaann bbee rree--ssttaarrtteedd
  104. 104. Cloning an organism
  105. 105. Cloned animals: (Reproductive Cloning) First cloned rabbit by Chinese scientists First cloned horse by Italian Scientists Snuppy: first cloned dog from South Korea. CC “CopyCat” First cloned cat from Texas. Ralph: The first cloned rat by French scientists
  106. 106. Tissue Culture • used to produce clones of a plant • More identical plants produced in a short time.
  107. 107. Genetically Engineering • Involves the insertion of DNA from one organism into another OR modification of an organism’s DNA in order to achieve a desired trait. + A strawberry = resistant to frost 4 5 Arctic fish DNA strawberry
  108. 108. The Benefits of Genetic Engineering 1. Human Insulin 2. Crops with herbicide resistance 3. Crops with virus resistance 4. Crops that are drought tolerant 5. Control the ripening of fruits 6. Crops with increased nutrition 7. Milk production in cows with hormones
  109. 109. Disadvantages of Cloning • No variation • Same level of resistance to diseases or pests • Danger: Entire population of clones could be eliminated if not resistant to new threat.
  110. 110. WITH CREDITS TO DR MARTHESE AZZOPARDI
  111. 111. CCoollcchhiicciinnee  Is made from autumn crocus (Colchicum autumnale) - poisonous Added to actively dividing cells to inhibit spindle formation
  112. 112. Chromatid pairs remain in their metaphase positions This technique enables the number and structure of chromosomes to be examined under the microscope
  113. 113. The DNA content of the cell as shown below is 10 units. What will the DNA content be at the end of mitosis?
  114. 114. DNA content and mitosis
  115. 115. DNA Content DNA duplication during interphase Mitosis 20 units 40 units 20 units 20 units
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