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Biology Class Topics & Objectives - January 6

Detailed class topics and objectives for a biology class on January 6, including assignments like the Lab phase of mitosis and Chapter 6 Quiz 2. Learners will explore meiosis vs. mitosis, genetic variation, and its importance in evolution.

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Biology Class Topics & Objectives - January 6

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  1. Hand in the Lab – How long is each phase of mitosis? and ALL chapter 6 corrections before the bell rings Chapter 6 Quiz 2 Begin Chapter 7 Stages of meiosis Meiosis vs. mitosis “That's what learning is, after all; not whether we lose the game, but how we lose and how we've changed because of it and what we take away from it that we never had before, to apply to other games. Losing, in a curious way, is winning.” Richard Bach To assess learning about Chapter 6 Title: Biology 1/11/07 Class Topics Objectives: Monday, January 6, 20208:42 AM

  2. Class Assignments What By When • Lab – How long is each phase of mitosis? 1/11/07 • Chapter 6 Quiz 2 1/11/07 • Read 144-149 1/16/07 • W.S. 7.1 (DR/Quiz) 1/16/07 • Due this class period • Due next class period • Due in the future

  3. Grade Sheet

  4. Changes and Postquiz Activities • Changes • # 9 • option d • G0, G1, G2, G3 • #28 • Do not do • #35 • Instructions should state that the answers can be labeled with the phases of mitosis as well as interphase • Hand in when completed • Read 144-149

  5. Meiosis • Process of cell division - chromosome number is halved • From 2n to n • Formation of gametes • Starts after G1, S, G2 • Chromosomes have been replicated • Sister chromatids (4 arms) • Two divisions • Meiosis I, Meiosis II

  6. Meiosis: step by step • Meiosis I • Prophase I (same as mitosis except…) • The chromosomes pair up with their homolog (the other of the homologous pair) to form tetrads • during synapsis (pairing up), crossing over can occur

  7. Meiosis: step by step • Metaphase I • homologous pairs line up along equator with spindle fibers attaching to only one side of each centromere • Anaphase I • The spindle fibers pull the homologous chromosomes to the separate poles • This gets the cell into the haploid state • Reduction division

  8. Meiosis: step by step • Telophase I • Cytokinesis occurs and two haploid cells with sister chromatids have been formed • Meiosis II • Prophase II • Occurs right after telophase I has finished. No interphase between the two

  9. Meiosis: step by step • Metaphase II • Haploid number of chromosomes line up along equator • Anaphase II • Sister chromatids separate • Telophase II • Cytokinesis occurs and cell enters interphase once more

  10. Mitosis no pairing of homologous chromosomes One division separation of chromatids Exact copy of original Diploid cells Meiosis homologous chromosomes paired form tetrads crossing over 2 divisions 1st reduction division 2nd separation of chromatids Genetic Variation Haploid cells Mitosis vs Meiosis

  11. Meiosis: Totals • Four cells • All Haploid • Gametogenesis • Males - all usually develop completely • Spermatogenesis – forms sperm • Females - usually only 1 develops • Oogenesis – forms ova

  12. From: http://www.accessexcellence.org/AB/GG/meiosis.html

  13. From: http://www.handsongenetics.com/meiosis.html

  14. Genetic variation • Allows for new genetic combinations • Unlike mitosis • 1. Independent assortment • Random distribution of homologous chromosomes • Each of the 23 pairs segregates independently • 223 combinations (8,388,608) from one cell

  15. Genetic variation (cont.) • 2. Crossing-over • Occurs during Prophase I when homologous chromosomes synapse • Trading of genetic material between homologous chromosomes (switching genes) • Increases genetic diversity

  16. Genetic variation (cont.) • 3. Random fertilization • Random fertilization means each gamete was independently assorted • (223 * 223) = 70,368,744,177,664 combinations

  17. Importance of genetic variation • Very important for evolution • change in characteristics of a population from one generation to the next • The pace of evolution can be sped up by increased genetic variation • Depends on natural selection

  18. Meiosis coloring • Choose four colors, one for each pair of homologous chromosomes • Draw in the chromosomes for all of the stages of meiosis using 8 chromosomes

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