Chapter 5 with ans

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Chapter 5 with ans

  1. 1. 1 © Gabriel Chua, 2013Chapter 5: Cell DivisionImportant terms and concept1. Haploid – Cell with single set of chromosome (n)2. Diploid – Cell with complete sets of chromosomes (2n)3. Cell division:a) Mitosis – 1 parent cell (2n)  2 identical daughter cells ( 2n )b) Meiosis – 1 parent cell (2n)  4 different daughter cells ( n )4.5.1) Mitosis1. 1 parent cell (2n)  2 identical daughter cells ( 2n )2. It is part of the cell cycle (Interphase  Mitosis  Cytokinesis)3. Interphase is divided into:a) G1 phase  Growth of cell by producing proteins and organellesb) S phase  Synthesis / duplication of DNA (thread-like chromatin)c) G2 phase  Growth of cell by producing proteins and organelles4. Mitosis is divided into prophase, metaphase, anaphase and telophasechromatid sister chromatidchromosome chromosomehomologous chromosome
  2. 2. 2 © Gabriel Chua, 2013Prophase  Chromosomes start to appear and condense as 2identical chromatids Nuclear membrane disintegrate and nucleolusdisappear Centrioles move apart to opposite sides Spindle fibre begins to formMetaphase  Chromosomes move to cell’s equator Chromosomes line up at cell’s equator with centromeresattached to spindle fibre Each chromatid faces its own poleAnaphase  Chromosomes divide into two Each sister chromatid separate and move to oppositepoles When the chromatids reached its own pole, they becomeindependent chromosomesTelophase  There are now 2 sets of chromosomes, one at each pole Chromosomes become thread-like structures Spindle fibre disappear Nuclear membrane begins to form around both sets ofchromosomes Nucleolus reappears Cytokinesis begins5. Cytokinesis in animal cells is by forming cleavage while that of plant cells is by formingcell plate.6. Importance of mitosisa) Repair damaged cells and replace dead cellsb) Asexual reproduction in unicellular organismsc) Preserve diploid number of chromosomed) Ensure new cells are identical to parent cells
  3. 3. 3 © Gabriel Chua, 20137. Application of mitosisa) Repair damaged cells and replace dead cellsb) Tissue culturec) Clonnnigd) Uncontrolled mitosis causes cancer5.2) Meiosis1. 1 parent cell (2n)  4 different daughter cells ( n )2. Meiosis is divided into:a) Meiosis I b) Meiosis II Prophase I  Prophase II Metaphase I  Metaphase II Anaphase I  Anaphase II Telophase I  Telophase IIProphase I  Chromosomes thickens and condense Each chromosome consists of 2 sister chromatids Homologous chromosomes pair together (bivalent) viasynapsis The criss-cross between homologous chromosomes isknown as chiasmata This results in genetic variation Centrioles move to opposite poles Spindle fibre forms Nuclear membrane and nucleolus disintegrateMetaphase I  Paired homologous chromosomes line up at cell’sequator Each chromosome are attached to spindle fibre atcentromeres Each chromosome faces its own poleAnaphase I  Paired homologous chromosomes separate from eachother and move to opposite pole
  4. 4. 4 © Gabriel Chua, 2013Telophase I  Chromosomes reached its own pole Each pole has haploid chromosome set Spindle fibre disappear Nuclear membrane and nucleolus reform Cytokinesis begins3. Meiosis II is the same as mitosis4. Importance of meiosisa) Allow trait inheritance in offspringb) Maintain same number of chromosomes in each generationc) Ensure production of haploid gametes in sexual reproductiond) Produce genetic variationComparison between Meiosis I and Meiosis IIMeiosis I Meiosis IISimilarities1. Consists of 4 stages, ie. prophase, metaphase, anaphase & telophase2. Involves division of nucleus and cytoplasmDifferencesYes, at Prophase I Synapsis NoYes, at Prophase I Crossing over NoIn metaphase I, pairedhomologous chromosomes /bivalent / tetrad line up atequatorMetaphaseIn metaphase II, sisterchromatids line up at equatorIn anaphase I, homologouschromosomes separate andmove to opposite sideAnaphase IIn anaphase II, sisterchromatids separate andmove to opposite side2 different daughter cells ( n )Number of daughter cells4 different daughter cells ( n )
  5. 5. 5 © Gabriel Chua, 2013Comparison between Meiosis and MitosisMeiosis MitosisSimilarities1. Both process are cell division process2. Chromosomes only replicate onceDifferencesReproductive cells Place occur Somatic cellsParent cells divide twice Number of division Parent cells divide once4 different daughter cells (n) Number of daughter cells 2 identical daughter cells(2n)Yes, at Prophase I Synapsis No2 Number of cytokinesis 1Yes, at Prophase I Crossing over NoEach daughter cell has halfthe number of chromosomeof parent cellNumber of chromosomes indaughter cellsEach daughter cell has thecomplete number ofchromosome as parent cellGenetic composition aredifferent to parent cell or toeach otherGenetic composition ofdaughter cellsGenetic composition areidentical to parent cell andeach otherOccurs during interphasebefore Meiosis I begins DNA replicationOccurs during interphasebefore mitosis begins Produce gametes Cause genetic variation Reduce number ofchromosomes to halfRole in animal body Produce cells forgrowth Asexual reproduction

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