1. Tuesday, November 22, 2016 1 Meiosis Packet #18 Chapter #6

2. Review of Reproduction 11/22/2016 2

3. Review Reproduction Cellular Asexual The Cell Cycle Sexual Meiosis Organism Asexual Budding Binary Fission Sexual Sex Occurs at two Levels. 11/22/2016 3

4. INTRODUCTION Tuesday, November 22, 2016 4

5. Important Info Two cell divisions Two cell divisions These two divisions result in four daughter cells These two divisions result in four daughter cells The ploidy changes unlike in the cell cycle The ploidy changes unlike in the cell cycle 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 Diploid cells become haploid cells Diploid cells become haploid cells Crossing over of genetic material occurs Crossing over of genetic material occurs Tuesday, November 22, 2016 5

6. Stages of Meiosis Interphase Interphase DNA Synthesis DNA Synthesis M1 (PMAT 1) M1 (PMAT 1) Meiosis 1 Meiosis 1 Separation of homologous pairs Separation of homologous pairs M2 (PMAT 2) M2 (PMAT 2) Meiosis 2 Meiosis 2 Separation of sister chromatids Separation of sister chromatids Stages of Meiosis Interphase Gap Phase 1 Synthesis (S) Phase Gap Phase 2 Meiosis 1 1 st Cell Division Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Meiosis 2 2 nd Cell Division Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Two Cell DivisionsTuesday, November 22, 2016 6

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. 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 Tuesday, November 22, 2016 9

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

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 Tuesday, November 22, 2016 11

12. Meiosis I Metaphase 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 Tuesday, November 22, 2016 12

13. Meiosis I Anaphase 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 Tuesday, November 22, 2016 13

14. Meiosis I Telophase 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 Tuesday, November 22, 2016 14

15. So Far… Tuesday, November 22, 2016 15

16. STEPS OF MEIOSIS MEIOSIS II Tuesday, November 22, 2016 16

17. 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 17

18. 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 Tuesday, November 22, 2016 18

19. 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 Tuesday, November 22, 2016 19

20. Review 11/22/2016 20

21. Review 11/22/2016 21 Stages of Meiosis Interphase Gap Phase 1 Synthesis (S) Phase Gap Phase 2 Meiosis 1 1 st Cell Division Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Meiosis 2 2 nd Cell Division Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Two Cell Divisions

22. Comparison of The Cell Cycle vs. Meiosis 11/22/2016 22

23. Comparison I Tuesday, November 22, 2016 23 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

24. Connecting the Cell Cycle & Meiosis Tuesday, November 22, 2016 24