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Meiosis

Meiosis. Katie Hughes, David Suarez, Abi Lawrence, Taylor Edwards and Katelynn Granger. Meiosis. 4.2.1: State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei.

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Meiosis

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  1. Meiosis Katie Hughes, David Suarez, Abi Lawrence, Taylor Edwards and Katelynn Granger

  2. Meiosis • 4.2.1: State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei. • Called reduction division because the daughter cells have only half of the number of chromosomes as the parent cell • Purpose: To produce gametes to facilitate sexual reproduction • Result: Four haploid cells • OVERVIEW: • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__stages_of_meiosis.html

  3. Meiosis • Spilt into 2 parts: • Meiosis I • Prophase • Metaphase • Anaphase • Telophase • Meiosis II • Prophase • Metaphase • Anaphase • Telophase

  4. Important definitions • Haploid-a cell having half the number of chromosomes than a somatic cell • Somatic cell- normal body cell • gamete- sex cell (sperm or egg cell) • Chiasmata-the site at which crossing over takes place. The process of crossing over

  5. Meiosis I • Interphase • Cell growth and DNA replication (review--before meiosis I) • Prophase I • Chromosomes condense • Homologous chromosomes pair up and crossing over occurs (the point of cross over is known as the chiasmata) • Nuclear membrane disintegrates and the centrioles travel to the poles of the cell

  6. Metaphase I • Microtubules form a spindle and the spindle fibers attach to the centromeres of the chromosomes • Pairs of homologous chromosomes align along the metaphase plate 

  7. Anaphase I • Spindle fibers shorten and pull paired chromosomes in opposite directions • Paired homologous chromosomes separate and pulled to opposite poles (sides) so that each pole contains one chromosome of each pair.

  8. Telophase I • A nuclear membrane forms around the chromosomes at each pole and chromosomes uncoil • Spindle fibers disintegrate • The cell undergoes cytokinesis to form two daughter cells (two haploid cells)  • At the end of telophase I the cells may enter a short interphase period or proceed directly to meiosis II • DNA is not replicated

  9. Meiosis II • Mostly the same!!! Except this time it involves half the number of chromosomes as Meiosis I • Prophase II • No crossing over (chiasma) • Metaphase II • SAME • Anaphase II • Separation of sister chromatids, instead of homologous chromosomes • Telophase II  • SAME RESULT: FOUR HAPLOID DAUGHTER CELLS. http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html

  10. http://www.johnkyrk.com/meiosis.html

  11. 10.1.2 Outline the formation of chiasmata in the process of crossing over

  12. Chiasmata • New combinations of genes within chromosomes are possible through this process • Can occur between any non-sister chromatids • During prophase I, chromatids are close together, so parts of each chromatid overlap, break at the chiasmata and reattach to the other chromatid • Sister chromatids a, b, c and d (b and c end up as new combinations called recombinants

  13. http://www.sumanasinc.com/webcontent/animations/content/independentassortment.htmlhttp://www.sumanasinc.com/webcontent/animations/content/independentassortment.html

  14. Meiosis • 10.1.3 Explain how meioisis results in an effectively infinite genetic variety in gametes through crossing over in prophase I and random orientation in metaphase I • The number of chiasmata, or points of crossing over, can differ…..infinite variety!!

  15. Mendel’s Law of Independent Assortment • 10.1.4 • States that any one of a pair of characteristics may combine with either of another pair. • So, two characteristics must be on different chromosomes • Since any combination of chromosomes is possible in metaphase I, any one pair of characteristics may combine with either of another pair

  16. Mitosis V. Meiosis • Takes place within somatic (body) cells • Results in 2 daughter cells • Mother cell can be haploid of diploid • Is preceded by a S-phase • No homologous pairing of chromosomes • Genotype of daughter cells are identical to mother cells • Takes place within gametes (sex cells) • Results in 4 haploid gametes • Mother cell is diploid • Only meiosis I preceded by a S phase • During prophase I, homologous chromosomes pair up • Meiotic products differ in their genotype from the mother cell

  17. WORKS CITED Works Cited "Chromosomes Crossing Over." Sciencelearn. University of Waikato, 8 June 2011. Web. 14 Feb. 2012. <http://www.sciencelearn.org.nz/Contexts/Uniquely-Me/Sci-Media/Images/Chromosomes-crossing-over>. Farabee, M.J. "CELL DIVISION: Meiosis..." Estrella Mountain Community College. 18 May 2010. Web. 10 Feb. 2012. <http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmeiosis.html>. Griffiths, Anthony J. F. An Introduction to Genetic Analysis. New York: W.H. Freeman, 2000. Print. Hill, McGraw. "Stages of Meiosis." Highered.mcgraw-hill.com. McGraw Hill. Web. 10 Feb. 2012. <http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio19.swf::Stages%20of %20Meiosis>. "IB Biology Notes - Meiosis." IB Guides - Free International Baccalaureate Study Guides, Notes, Videos and Powerpoints. Web. 10 Feb. 2012. <http://www.ibguides.com/biology/notes/meiosis>. Khara, Kanika. "Difference Between Mitosis and Meiosis." Buzzle Web Portal: Intelligent Life on the Web. Buzzle. Web. 14 Feb. 2012. http://www.buzzle.com/articles/difference-between-mitosis-and-meiosis.html . Kyrk, John. "Meiosis = Double Cell Division." Communicating at an Unknown Rate. 2012. Web. 14 Feb. 2012. <http://www.johnkyrk.com/meiosis.html>. Peeters, WeemMinka., Christopher Talbot, and Anthony Mayrhofer. Biology. Melton: Ibid, 2007. Print. "Phases of Meiosis | Biology." Khan Academy. Web. 10 Feb. 2012. <http://www.khanacademy.org/video/phases-of-meiosis?topic=biology>.

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