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Note On Cell And Nuclear Division

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Published in: Biology
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Biology Cell and Nuclear division

Areesha A / Dubai

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  1. Cell and Nuclear Division Cha ter 5
  2. Content Replication and division of nuclei and cells Understanding of chromosome behavior in mitosis
  3. â1SVHdVNV 3SVHdV.LQ11.N aSVHdCY1'JL S VHcN3LN1 SVHdOHd QISVHdONd SISC)LIVN
  4. aus eggs fish hen hatches eggs f c+hor rnother small fish The size of living things changes as time goes by human chick animal babu plant All living organisms, grow, repair themselves and reproduce.
  5. Living organisms are made out of cells, this means that cells must be able to grow and reproduce too
  6. The cen Nucleus Nucleolus Chromosomes Nucleus Plasma membrane Nuclear Envelope Nuclear Chromatin Daughter Cells One of the most conspicuous structures in eukaryotic cell is the nucleus. Its importance has been obvious ever since it was realized that the nucleus always divides before the cell divides
  7. Introduction The cell Nucleus Nuclear Nucleolus Envelope Nuclear Chromosomes Chromatin The nucleus is responsible for the cells activities and does so through DNA. All cells in an organism are genetically identical. Cells arise from pre- existing cells and we are going to see how in this chapter.
  8. Walther Flemming investigated the process of cell division and the distribution of chromosomes to the daughter nuclei, a process he called mitosis from the Greek word for thread.
  9. The nucleus contains chromosomes Chromosomes are thread-like structures found within the nucleus The number of chromosomes in a cell is characteristic of the species - for example, we humans have 46 of them.
  10. gettyima e. SEM of chromosome set from human male x2,100 (Colour Enhanced) Humans have 46 chromosomes (23 pairs) including two sex chromosomes (X and Y for males). A photograph of chromosomes taken from an electron microscope is known as a karyotype. A karyotype is the complete set of chromosomes of an organism.
  11. Animals have two sets of matching chromosomes, and as such their cells (except for reproductive cells, gametes) are called diploid. 13 19 15 14 10 17 16 21 12 18 xy
  12. Matchinq pairs of chromosomes are called homologous pairs. Each pair is given a number. One pair from the father (paternal) and a pair from the mother (maternal).
  13. Gametes, which only have one set of chromosomes are described as haploid cells. In humans, a diploid cell has 46 chromosomes and a haploid cell has 23 12 13 15 20 16 22 SCIENCEDhOtOLlBRAm
  14. 15 14 13 19 EXR 18 17 16 21 xy Autosomes - numbered chromosomes Sex chromosomes - sex determining factor
  15. Learning Objectives Explain the meanings of the terms haploid and diploid and the need for a reduction division (meiosis) prior to fertilization in sexual reproduction.
  16. Explain the need for the production of genetically identical cells and the fine control of replication.
  17. Haploid and diploid cells Cells that contain two sets of chromosomes are called diploid cells.(2n) In humans (46) 1
  18. Haploid and diploid cells Gametes are cells that only contain one set of chromosomes. These cells are haploid. (n) In humans (23)
  19. A chromosome is composed of two identical chromatids attached by a centromere. Each chromatid is made up of tightly wound DNA wrapped around histones. During cell division, spindle fibers attach to the kinetichore. One DNA molecule for each chromatid. Kinetochore Centromere
  20. Structure of the chromosome Image taken from http://ndsfornys. com (blogs/ blog/ 2010/10/23/1ets -wrap-this-up/ Each chromosome has a characteristic set of genes which code for different feature. E.g., the gene responsible for the genetic disease cystic fibrosis is located on chromosome number 7
  21. Gene 2 DNA Chromosome Genes Genes are genetic material on a chromosome that code for a trait. For example, vou have a gene for eye color. Alleles are variations of genes. For example, you have the allele for brown eye color. Note that some alleles are dominant over others. That is, if a person inherits both the dominant and the recessive alleles, the dominant allele will be the one expressed.
  22. Mitochondria Nucleus reticult.rn Golø Chromosome Human cell Chromatid Telomere Cilia Cell mern&ane ts"cleotide Thymine DNA (double helix) backbone virtualmedicalcentre.com
  23. Genes for different traits - each chromosome is made up of several thousand genes Centromere holds the 2 chromatids together 2 identical sister chromatids, each made of one DNA molecule, make one chromosome
  24. Homologous Pair of Chromosomes Ge ne for eye co Gene for e nzyme A .......................+ Gene for cytochrome C ..................+ A duplicated chromosome (came from mother) A duplicated chromosome (came from father) The gene for a particular characteristic is always found in the same location (address) or locus (loci, plural) on a chromosome.
  25. Homologous Pair of Chromosome Homologous: similar in structure and composition. A gene controlling a characteristic may exist in different forms (alleles) which are expressed differently. (pg 79)
  26. Cystic fibrosis is caused by a faulty allele in a gene that codes for a chloride channel protein that produces normal mucus, The mutated allele causes very thick mucus to be produced indeed, leading to cystic fibrosis.. one homologous pair of chromosome 7 or or locus for cystic fibrosis gene sufferer carrier cystic fibrosis allele normal normal allele
  27. one homologous pair of chromosome 7 or locus for cystic or fibrosis gene Only when both homologous chromosomes have a copy of the faulty allele will the person be a victim of the disease - if not, the person will simply be a carrier sufferer carrier cystic fibrosis allele normal normal allele
  28. Strictly Analogies ONLY Nucleus: The cabinet Locus: The drawers Genes: The Files Chromosomes (DNA): The information Homologous pair: A pair of twins Alleles: Isotopes of the same element
  29. Nuclear Division Growth Sexual Reproduction
  30. Growth When a diploid zygote (one cell) grows into a multi-cellular diploid adult Daughter cells must keep the same number of chromosomes as the parent cells. Nuclear division: Mitosis
  31. Sexual Reproduction The number of chromosomes is halved Meiosis is used for sexual reproduction, and the resultant cell is a gamete - a haploid cell (gametes) with half the full number of chromosomes. Daughter Nucl ill Interphase Meiosis I Homologous Chromosomes Dau hter Nuc ei Meiosis Il
  32. Diploid Mitosis zypte syngamy Haploid Meiosis
  33. Nuclear Division Growth Sexual Reproduction
  34. Learning Objective Describe with the aid of diagrams the behavior of chromosomes during the mitotic cycle and the associated behavior of the nuclear envelope, cell membrane, centrioles and spindle (names of main stages).
  35. Mitosis A nuclear division Produces two genetically identical daughter nuclei Containing same number of chromosome as the parent nucleus. Part of the cell cycle.
  36. Part of the cell cycle Nuclear division Mitosis Same no. of chromosome with parent nucleus two genetically identical daughter nuclei
  37. Cell Cycle The period between one cell division and the next Mitotic cell cycle DNA replication cell division Nuclear divison by mitosis Interphase
  38. Mitotic cell cycle DNA replication Cell division Nuclear divison by mitosis Interphase Cell cycle has 3 phases: Interphase, nuclear division and cell division.
  39. Cell Cycle: Interphase The cell re-grows to its normal size following cell division and then carries on its normal processes (e.g., synthesize proteins). When a signal is received to divide, the DNA replicates so that each chromosome consists of two identical chromatids.
  40. Mitotic cell cycle DNA replication Cell division Nuclear divison by mitosis Interphase
  41. 4 stages in Mitosis Prophase Metaphase Anaphase Telophase
  42. Prophase The chromatin condenses into a highly ordered structure called chromosomes and the nuclear membrane begins to breakup. The nucleus also breaks up and forms part of several chromosomes. Centrioles move to opposite poles of nucleus.
  43. Early prophase centriole replicates just before prophase plasma membrane cytoplasm nucleolus nuclear envelope chromosomes start to coil up, becoming shorter and thicker; they become visible because they stain more intensely
  44. Late prophase 4, centrioles moving to opposite ends (poles) of nucleus nuclear envelope 'disappears' (it breaks up into small vesicles which are not visible with a light microscope) nucleolus 'disappears' (forms part of several chromosomes) two chromatids make one chromosome cen tromere At the end of prophase a spindle is formed (see below).
  45. Metaphase Condensed chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells.
  46. Metaphase each centriole reaches a pole; they help to organise production of the spindle microtubules spindle (made from protein microtubules) chromosomes line up across the equator of the spindle; they are attached by their centromeres to the spindle
  47. each chromosome splits at the centromere the chromatids are pulled apart
  48. Anaphase Chromatids (identical copies of chromosomes) separate as they are pulled towards opposite poles within the cell. They are pulled because the microtubule fibres begin to shorten, pulling them along.
  49. Anaphase chromatids move to opposite poles, centromeres first, pulled by the microtubules
  50. Telophase Nucleus, nucleolus reforms and chromosomes unravel into longer chromatin structures for reentry into interphase. Cytokinesis also occurs - the division of cytoplasm and cell into two by constriction from edges of cell.
  51. Telophase nucleolus re-forming remains of spindle which is breaking down nuclear envelope re-forming chromatids have reached the poles of the spindle; they will now uncoil again to form chromatin (each chromatid contains one DNA molecule which will replicate itself during interphase before the next division) cytokinesis — this is division of the cytoplasm and cell into two by constriction from the edges of the cell plasma membrane centriole — will replicate during interphase before the next nuclear division
  52. Cytokinesis cyto- (cell) and kinesis (motion, movement) the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. initiates during the late stages of mitosis, and sometimes meiosis, splitting a binucleate cell in two, to ensure that chromosome number is maintained from one generation to the next.
  53. An electron micrograph image of a cell that has almost completed cell division and cytokinesis. Mitosis has already been completed. An arrow points to a centrosome still present near one of the nuclei.
  54. Oogonium Primary Secondary Female Meiosis begins Meiosis I Meiosis 11 Polar Polar body ies Differentiation Normal process of cytokinesis is oogenesis (the creation of an ovum in the ovarian follicle of the ovary), where the ovum takes almost all the cytoplasm and organelles, leaving very little for the resulting polar bodies, which then die.
  55. In plant cells, a dividing structure known as the cell plate forms across the centre of the cytoplasm and a new cell wall forms between the two daughter cells. 100 Cleavage furrow a Cleavage of an animal cell SEM) Vesicles wall of forming parent cell 1 pm Daughter cells (b) Cell plate formation in a plant cell (TEM)
  56. Why Mitosis?
  57. Asexual reproduction Mitosis process of growth and repair of multicellular organisms
  58. Mitosis's Role Process of growth and repair of multicellular organisms Each new daughter cell receives the same number and kind of chromosomes as the mother cell; Daughter cell are genetically identical to their mother cell and to each other.
  59. Process of growth and repair of multicellular organisms Replacement of cells and repair of tissues. E.g.: rapid cell replacement in the lining of the gut E.g.: the starfish can regenerate the whole arm.
  60. Mitosis Asexual reproduction Production of a new individual by one parent organism. Offspring are clones of their parents.
  61. binary fission single-celled organisms (e.g. a) amoeba) reproduce simply by splitting into two new cells. b) budding bud on parent organism (e.g. yeast) develops into a new organism through repeated cell divisions. A new organism grows on another one c) vegetative reproduction plants send out stolons (above ground) or (underground) which become new individuals e.g. strawberries, Bermuda grass, ferns,
  62. Binary fission Prokaryotic chromosome Plasma membrane Cell wall Duplication of chromosome Continued growth of the cell Division into two cells
  63. Vegetative reproduction from a stem cutting less than a week old. Some species are more conducive to this means of propagation than others.
  64. Production of new individuals along a leaf margin of the air plant, Ka/anchoe pinnata The small plant in front is about 1 cm tall. The concept of "individual" is obviously stretched by this process.
  65. A Muscari, or bulb, displaying vegetative reproduction.
  66. The budding of yeast, (Saccharomyces cerevisae)
  67. SCIENCE hotOLlBRARY Light micrograph of a freshwater coelenterate polyp, Hydra sp., asexually reproducing by budding off a daughter polyp. The anterior of the creature consists of a mouth surrounded by tentacles. These capture food such as small water fleas and algal cells which float past on the current.
  68. Learning Objective Explain how uncontrolled cell division can result in cancer and identify factors that can increase the chances of cancerous growth.
  69. Cancer/Carcinoma Cancer is a common disease in developed countries There are many different forms of cancer.
  70. Cancer is a result of uncontrolled mitosis, that is to say that they divide repeatedly and are out of control. This uncontrolled mitosis produces an irregular mass of cells known as a tumour, and these cells are usually abnormal in shape. (Cancererous cells splitting apart)
  71. Normal Calb Strutture Cancer N l*algi$ — Sirio' I — Cwr:se
  72. Cancer Cancers are as a result of mutation to the genes that control cell division, and divide continuously from there, passing the mutated gene to all its descendants.
  73. A mutated gene that causes cancer is known as oncogene. A change in a gene is called mutation Mutations happens usually but are inhibited in some way which caused early death of these cells or are destroyed by the immune system, Cancer cell under attack by the immune system
  74. A single mutation cannot cause cancer, but several independent rare 'accidents' must all occur in one cell
  75. Viruses Radiation Carcinogens Hereditary Predisposition Chemicals
  76. Carcinogen There are many different reasons that a gene may mutate, and any factor that may cause it to do so is known as a mutagen - several of them at once are thought to have to happen in one cell. A carcinogen is an agent that causes cancer, and some mutagens are carcinogenic.
  77. Viruses Radiation Carcinogens Hereditary Predisposition Chemicals
  78. Radiation X-rays, radioactive decay elements and gamma rays can all form damaging ions inside cells which can break dna strands. UV light can damage genes, potentially causing skin cancer. Chemicals Chemicals in tar from cigarettes or cigars is an extremely common killer - 25% of all cancer deaths are due to tar carcinogens. These chemicals can damage DNA molecules. Viruses More rarely, cancers can be caused by viruses, including Pallipoma, a virus that can be transmitted sexually and has been linked to cervical cancer. Hereditary Predisposition A person do not inherit cancer, but you can inherit faulty genes that cause it, or simply a great susceptibility to developing cancer.
  79. Carcinogens cause mutations e.g. tJV light tar in tobacco asbestos X-rays absorption of nutrients o O o DOC I 2 4 Oncogenes transformed by carcinogens. Cancerous cell does not respond to signals from other cells so continues to divide. Mitosis. Cancerous cells not removed by immune system. Rapid mitosis.
  80. O 6 Tumour gets bigger. Cells change their characteristics and 100k different under the microscope. 7 Tumour supplied with blood and lymph vessels. Tumour cells spread in blood and lymph to other parts Of the body. 8 Metastasis. Tumour cells invade Other tissues. Secondary cancers form throughout the body.
  81. Primary Growths Primary growths are small groups of tumour cells. Both tumour types place a huge drain on the bodys resources because of the constant cell division.
  82. Benign Primary Growth Malignant
  83. Tumors Benign Do not spread from origin Compress and displace surrounding tissues
  84. Tumor Malignant Far more dangerous Spread through body, invade tissues and destroy them. Distributed around the body via blood stream Interfere with the functioning of the area where they started to grow. Cancerous cells can break off and spread through the blood and lymphatic system to other parts of the body to form secondary growths.
  85. Telomere and aging https://learn.genetics.utah.edu/content/basics/t elomeres/ https://www.youtube.com/watch?v=SHyTlhL1 CfY Nobel laureate Dr Elizabeth Blackburn explains how the ends of our chromosomes are linked to ageing in the 2013 Schrödinger lecture. https://www.scientificamerican.com/article/how- to-control-aging/
  86. DNA packaging in the Nucleus 2 meters of DNA inside the nucleus of a cell 10 micrometer in diameter. https://www.biointeractive.org/classroom- resources/ how-dna-packaged
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