1. Tuesday, November 22, 2016 1 Meiosis Packet #18

2. INTRODUCTION Tuesday, November 22, 2016 2

3. Tuesday, November 22, 2016 3 Introduction I Two cell divisions Two cell divisions These two divisions result in four daughter cells These two divisions result in four daughter cells The daughter cells have half the number of chromosomes that the parent cell had The daughter cells have half the number of chromosomes that the parent cell had Move from a diploid cell to a haploid cell Move from a diploid cell to a haploid cell Diploid stem cell to a haploid sex cell Diploid stem cell to a haploid sex cell Crossing over of genetic material occurs Crossing over of genetic material occurs

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5. Tuesday, November 22, 2016 5 Stages of Meiosis Interphase Interphase DNA Synthesis DNA Synthesis M1 (PMAT 1) M1 (PMAT 1) Meiosis Phase 1 Meiosis Phase 1 Separation of homologous pairs Separation of homologous pairs M2 (PMAT 2) M2 (PMAT 2) Meiosis Phase 2 Meiosis Phase 2 Separation of sister chromatids Separation of sister chromatids

6. Tuesday, November 22, 2016 6 Question 1. During which process(es)/steps are sister chromatids seperated a. Cell Cycle b. Meiosis I c. Meiosis II d. A & B are correct e. B & C are correct f. A & C g. All of the above are correct h. None of the above is correct

7. Vocabulary Homologous Homologous Similar by virtue of a common evolutionary origin. Homologous genes or proteins generally show similarities in their sequence. Similar by virtue of a common evolutionary origin. Homologous genes or proteins generally show similarities in their sequence. Homologous Chromosome Homologous Chromosome One of two copies of a particular chromosome in a diploid cell, one from the father and one from the mother. One of two copies of a particular chromosome in a diploid cell, one from the father and one from the mother. Homologous Pair Homologous Pair Both copies of chromosomes (one from the father and mother). Both copies of chromosomes (one from the father and mother). Tuesday, November 22, 2016 7

8. STAGES OF MEIOSIS Interphase Tuesday, November 22, 2016 8

9. Tuesday, November 22, 2016 9 Interphase Chromosomes are replicated Chromosomes are replicated Similar to what is seen during the Cell Cycle Similar to what is seen during the Cell Cycle G1, S and G2 phase occur G1, S and G2 phase occur

10. STAGES OF MEIOSIS MEIOSIS I Tuesday, November 22, 2016 10

11. Tuesday, November 22, 2016 11 Meiosis I 1st Cell Division Prophase 1 Prophase 1 Chromosomes condense Chromosomes condense Homologous chromosomes come together Homologous chromosomes come together Once the homologous pairs are together, chiasmata (chiasma {singular} ) form. Once the homologous pairs are together, chiasmata (chiasma {singular} ) form. Crossing over of genetic material occur at the chiasmata Crossing over of genetic material occur at the chiasmata Can last for days--or longer Can last for days--or longer

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13. Tuesday, November 22, 2016 13 Meiosis I Metaphase I Metaphase I Homologous pairs align at equatorial planes Homologous pairs align at equatorial planes Known as tetrads Known as tetrads Paired chromosomes line up in the middle and separate Paired chromosomes line up in the middle and separate

14. Tuesday, November 22, 2016 14 Question Which phase is the longest phase of Meiosis (entire process)? Which phase is the longest phase of Meiosis (entire process)? a. Prophase b. Prophase I of Meiosis II c. Prophase II of Meiosis II d. Prophase I of Meiosis I e. Prophase II of Meiosis I f. Two of the above are correct g. Three of the above are correct h. None of the above are correct

15. Tuesday, November 22, 2016 15 Question a. At the end of Meiosis I, which of the following is correct? a. Two Diploid cells are produced b. One Diploid cell is produced c. Four Diploid cells are produced d. Two Haploid cells are produced e. One haploid cell is produced f. Four haploid cells are produced g. None of the above is correct

16. Tuesday, November 22, 2016 16 Potential Exam Questions What align along the middle of the cell of What align along the middle of the cell of Metaphase of the Cell Cycle Metaphase of the Cell Cycle Metaphase I of Meiosis I Metaphase I of Meiosis I Metaphase II of Meiosis II Metaphase II of Meiosis II

17. Tuesday, November 22, 2016 17 Meiosis I Anaphase I Anaphase I Homologous pairs are separated and pulled to opposite poles Homologous pairs are separated and pulled to opposite poles Sister chromatids are pulled to the poles of the cell Sister chromatids are pulled to the poles of the cell However, the sister chromatids stay together However, the sister chromatids stay together Centromeres do not divide Centromeres do not divide

18. Tuesday, November 22, 2016 18 Meiosis I Telophase I & Cytokinesis Telophase I & Cytokinesis Cleavage furrows form in animal cells Cleavage furrows form in animal cells Cell plates form in plant cells Cell plates form in plant cells Nuclear envelope and nuclei re-form in some cells Nuclear envelope and nuclei re-form in some cells Sister chromatids are still joined together Sister chromatids are still joined together There is no further replication of genetic material before the 2nd cell division There is no further replication of genetic material before the 2nd cell division

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20. STEPS OF MEIOSIS MEIOSIS II Tuesday, November 22, 2016 20

21. Meiosis II 2nd Cell Division Prophase II Prophase II Spindle apparatus forms and chromosomes progress towards the equatorial plane Spindle apparatus forms and chromosomes progress towards the equatorial plane Metaphase II Metaphase II Sister chromatids arrange themselves on the equatorial plane (middle) of the cell Sister chromatids arrange themselves on the equatorial plane (middle) of the cell Tuesday, November 22, 2016 21

22. Tuesday, November 22, 2016 22 Meiosis II Anaphase II Anaphase II Sister chromatids are pulled to opposite poles by spindle fibers Sister chromatids are pulled to opposite poles by spindle fibers Centromeres divide Centromeres divide Sister chromatids are finally separated Sister chromatids are finally separated

23. Tuesday, November 22, 2016 23 Question When are centromeres divided? When are centromeres divided? a. Metaphase of the Cell Cycle b. Anaphase of the Cell Cycle c. Metaphase II of Meiosis I d. Metaphase I of Meiosis II e. Anaphase I of Meiosis II f. A & B are correct g. B & C are correct h. Three of the above are correct i. All of the above are correct j. None of the above is correct

24. Tuesday, November 22, 2016 24 Meiosis II Telophase II & Cytokinesis Telophase II & Cytokinesis Nuclei form at opposite poles of the cell Nuclei form at opposite poles of the cell Cytokinesis occur Cytokinesis occur Four daughter cells with a haploid number of chromosomes Four daughter cells with a haploid number of chromosomes

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27. Tuesday, November 22, 2016 27 Comparison Distinct Differences Key Concepts* Meiosis = 4 progeny cells [1 = 2 = 4]... thus 2 divisions Mitosis = 2 daughter cells only... thus 1 cell division Meiosis = one-half number of chromosomes Mitosis = same # of chromosomes as parent cell Meiosis = new combinations of gene not in parents & chromosomes sort randomly of each other Mitosis = daughter cells are genetically identical