meiosis powerpoint presentation

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  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    1. Consider helping students through mitosis and meiosis by developing an analogy to pairs of shoes. In this case, any given species has a certain number of pairs of shoes, or homologous chromosomes.
    2. In the shoe analogy, females have 23 pairs of matching shoes, while males have 22 matching pairs and 1 odd pair . . . maybe a sandal and a sneaker!
    3. You might want to get your students thinking by asking them why eggs and sperm are different. (This depends upon the species, but within vertebrates, eggs and sperm are specialized for different tasks. Sperm are adapted to move to an egg and donate a nucleus. Eggs contain a nucleus and most of the cytoplasm of the future zygote. Thus eggs are typically larger, nonmotile, and full of cellular resources to sustain cell division and growth.)
  • Figure 8.12A The human life cycle
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    1. Consider helping students through mitosis and meiosis by developing an analogy to pairs of shoes. In this case, any given species has a certain number of pairs of shoes, or homologous chromosomes.
    2. In the shoe analogy, females have 23 pairs of matching shoes, while males have 22 matching pairs and 1 odd pair . . . maybe a sandal and a sneaker!
    3. You might want to get your students thinking by asking them why eggs and sperm are different. (This depends upon the species, but within vertebrates, eggs and sperm are specialized for different tasks. Sperm are adapted to move to an egg and donate a nucleus. Eggs contain a nucleus and most of the cytoplasm of the future zygote. Thus eggs are typically larger, nonmotile, and full of cellular resources to sustain cell division and growth.)
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    Challenge students to identify which stage of meiosis is most like mitosis. Comparing the specific events of mitosis, meiosis I, and meiosis II to each other allows students to identify essential differences.
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    Challenge students to identify which stage of meiosis is most like mitosis. Comparing the specific events of mitosis, meiosis I, and meiosis II to each other allows students to identify essential differences.
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    Challenge students to identify which stage of meiosis is most like mitosis. Comparing the specific events of mitosis, meiosis I, and meiosis II to each other allows students to identify essential differences.
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    Challenge students to identify which stage of meiosis is most like mitosis. Comparing the specific events of mitosis, meiosis I, and meiosis II to each other allows students to identify essential differences.
  • Student Misconceptions and Concerns
    Students might not immediately see the need for meiosis in sexual reproduction. Consider an example of what would happen over many generations if gametes were produced by mitosis. The resulting genetic doubling is prevented if each gamete has only half the genetic material of the adult cells.
    Teaching Tips
    Challenge students to identify which stage of meiosis is most like mitosis. Comparing the specific events of mitosis, meiosis I, and meiosis II to each other allows students to identify essential differences.
  • Teaching Tips
    1. If you wish to continue the shoe analogy, crossing over is somewhat like exchanging the shoelaces in a pair of shoes (although this analogy is quite limited). A point to make is that the shoes (chromosomes) before crossing over are what you inherited . . . either from the sperm or the egg; but, as a result of crossing over, you no longer pass along exactly what you inherited. Instead, you pass along a combination of homologous chromosomes (think of shoes with switched shoelaces). Critiquing this limited analogy may also help students to think through the process of crossing over.
    2. In the shoe analogy, after exchanging shoelaces, we have “recombinant shoes”!
    3. Challenge students to consider the number of unique humans that can be formed by the processes of the independent orientation of chromosomes, random fertilization, and crossing over. Without crossing over, we already calculated over 70 trillion possibilities. But as the text notes in Module 8.17, there are typically one to three crossover events for each human chromosome, and these can occur at many different places along the length of the chromosome. The potential number of combinations far exceeds any number that humans can comprehend, representing the truly unique nature of each human being (an important point that delights many students!)
  • Teaching Tips
    1. If you wish to continue the shoe analogy, crossing over is somewhat like exchanging the shoelaces in a pair of shoes (although this analogy is quite limited). A point to make is that the shoes (chromosomes) before crossing over are what you inherited . . . either from the sperm or the egg; but, as a result of crossing over, you no longer pass along exactly what you inherited. Instead, you pass along a combination of homologous chromosomes (think of shoes with switched shoelaces). Critiquing this limited analogy may also help students to think through the process of crossing over.
    2. In the shoe analogy, after exchanging shoelaces, we have “recombinant shoes”!
    3. Challenge students to consider the number of unique humans that can be formed by the processes of the independent orientation of chromosomes, random fertilization, and crossing over. Without crossing over, we already calculated over 70 trillion possibilities. But as the text notes in Module 8.17, there are typically one to three crossover events for each human chromosome, and these can occur at many different places along the length of the chromosome. The potential number of combinations far exceeds any number that humans can comprehend, representing the truly unique nature of each human being (an important point that delights many students!)
  • meiosis powerpoint presentation

    1. 1. GRADE 12: MEIOSIS
    2. 2. © 2012 Pearson Education, Inc.
    3. 3. Why do gonosome undergo meiosis? Why do meiosis? Meiosis is “REDUCTION DIVISION”so Reduces chromosome number, parent cell is 2n while daughter cells are n.
    4. 4. Haploid gametes (n = 23) A life cycle n Egg cell n Sperm cell Meiosis Ovary Fertilization Testis Diploid zygote (2n = 46) 2n Key Multicellular diploid adults (2n = 46) Mitosis Haploid stage (n) Diploid stage (2n)
    5. 5. © 2012 Pearson Education, Inc.
    6. 6. QUIZ TIME… 1. In streptomycin fungus n = 11. What is the diploid number for this species? 2. If a horse egg has 98 chromosomes how many does a horse egg cell have? 3. If n = 16 for goldfish how many chromosome in a fin cell? 4. If 2n = 108 for black spruce trees then what is the haploid number? 2n = 14 for this species. Fill in the chromosome numbers for A each cell. B C What is process A, B, and C?
    7. 7. Sex Chromosomes XX chromosome - female XY chromosome - male
    8. 8. Meiosis I (four phases) • Cell division that reduces the chromosome number by one-half. • four phases: phases a. prophase I b. metaphase I c. anaphase I d. telophase I
    9. 9. Interphase I
    10. 10. Interphase I chromatin nuclear membrane cell membrane nucleolus
    11. 11. MEIOSIS I : prophase i
    12. 12. MEIOSIS I : prophase i © 2012 Pearson Education, Inc.
    13. 13. Metaphase I • Shortest phase • Tetrads align on the metaphase plate. plate • INDEPENDENT ASSORTMENT OCCURS: 1. Orientation of homologous pair to poles is random. 2. Variation 3. Formula: 2n Example: 2n = 4 then n = 2 thus 22 = 4 combinations
    14. 14. Metaphase I OR metaphase plate metaphase plate
    15. 15. Anaphase I • Homologous chromosomes separate and move towards the poles. • Sister chromatids remain attached at their centromeres. centromeres
    16. 16. Anaphase I
    17. 17. Meiosis i: telophase i © 2012 Pearson Education, Inc.
    18. 18. Meiosis ii © 2012 Pearson Education, Inc.
    19. 19. Meiosis ii: prophase II © 2012 Pearson Education, Inc.
    20. 20. Prophase II • same as prophase in mitosis
    21. 21. Metaphase II metaphase plate metaphase plate
    22. 22. Anaphase II
    23. 23. Telophase II
    24. 24. Crossing over © 2012 Pearson Education, Inc.
    25. 25. Crossing over © 2012 Pearson Education, Inc.
    26. 26. Non-disjunction = Nonseparation of chromoso mes resulting in diploid or empty gametes.
    27. 27. Conditions caused by non-disjunction Downs syndrome = Trisomy 21 - 3 copies of chromosomes 21 equalling a total of 47 chromosomes. = 2n + 1(chance of occurring in oogenesis increases with maternal age) Turners syndrome = Monosomy X - has only one X chromosomes totalling only 45 chromosomes in her body cells. (monosomy X) = 2n-1 Klinefelter’s syndrome = XXY - male which has an extra X chromosome = 2n + 1
    28. 28. Down’s syndrome – trisomy 21 A simple check for the presence of a bone in the nose could more accurately test unborn babies for Down's syndrome, scientists say. Researchers say combining the nose test with existing screening methods (amniocentesis, CVS) could lead to a five-fold reduction in the number of miscarriages linked to an invasive procedure used to confirm Down's syndrome.
    29. 29. Klinefelter’s syndrome XXY Normal boy who develops some female secondary sex character-istics at puberty. -slightly lower IQ, infertile, delayed motor, speech, maturation -treated with

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