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PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics

PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics. Number of different chromosomes in a species: n = haploid number. Most eukaryotes have two of each of its different types of chromosome in each of its cells. Thus, they have 2 n chromosomes per cell.

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PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics

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  1. PCB 3063 General Genetics Lecture Topic 3: Chromosome Mechanics

  2. Number of different chromosomes in a species: n = haploid number Most eukaryotes have two of each of its different types of chromosome in each of its cells. Thus, they have 2n chromosomes per cell. 2n is its diploid number Klug, Cummings, and Spencer, 8th ed.

  3. centromere homologous chromosomes metacentric acrocentric telocentric non-homologous chromosomes Human Mitotic ChromosomesFigure 2-4 Klug, Cummings, and Spencer, 8th edition

  4. more mitotic divisions plus growth and differentiation 1n fusion of gametes mitosis 2n meiosis of specialized germ cells mitosis 2n 2n 2n 2n fertilized egg 2n 2n fertilized egg 1n 2n mature (?) human with trillions of diploid cells, each derived by mitosis from original fertilized egg gametes interphase mitosis G1 S G2 M cytokinesis The Human Life Cycle

  5. Mitosis of a Cell with a Diploid Number of 4 Fig. 2-8 Klug and Cummings, 7th edition Similar to Fig. 2-7, 8th edition

  6. MEIOSIS Diploid to haploid state Single round replication followed by two cell divisions Meiosis I and Meiosis II

  7. The Stages of Meiotic Prophase I Fig. 2-13 Klug and Cummings, 7th edition Similar to Fig. 2-9 Klug, Cummings, and Spencer, 8th edition early prophase I mid prophase I late prophase I

  8. The Synaptonemal Complex Fig. 2-14 Klug, Cummings, and Spencer, 8th edition

  9. Completion of Meiosis Fig. 2-14 Klug and Cummings, 7th edition Similar to Fig. 2-10 Klug, Cummings, and Spencer, 8th ed. paired chromosomes lined up at metaphase plate separation of homologues – reductional division products of meiosis I already haploid – count centromeres! sister chromatids separate 4 haploid products

  10. interphase (G1) b b early prophase I a a B B a A b late prophase I B B a A a A metaphase I b b B a B b A b B b b B b A B A A A a A b A A a a anaphase I b b A A A A a a metaphase II B B B B b b final products B B a a a a independent assortment segregation

  11. Gametogenesis Fig. 2-15 Klug and Cummings, 7th edition Similar to Fig. 2-11 Klug, Cummings, and Spencer, 8th edition diplonema of prophase I ovulation penetration

  12. A Homologous Pair of Lampbrush Chromosomes from the Newt Alberts et al., Molecular Biology of the Cell, 3rd edition

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