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Chromosomes, Mitosis, and Meiosis

Chromosomes, Mitosis, and Meiosis. Cells Basic unit of life Essential link between generations Genomes Even simplest cell contains DNA, collectively called the organism’s genome Organized into genes. Prokaryotic cells Circular DNA molecules Eukaryotic cells

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Chromosomes, Mitosis, and Meiosis

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  1. Chromosomes, Mitosis, and Meiosis

  2. Cells • Basic unit of life • Essential link between generations • Genomes • Even simplest cell contains DNA, collectively called the organism’s genome • Organized into genes

  3. Prokaryotic cells • Circular DNA molecules • Eukaryotic cells • Chromosome packaging facilitated by histones • Histones form nucleosomes • Scaffolding proteins maintain chromosome structure

  4. Nucleosomes

  5. Mouse metaphase chromosome depleted of histones

  6. Eukaryotic cell cycle • Beginning of one division to beginning of next • Stages in eukaryotic cell cycle • Interphase • First gap phase • Synthesis phase • Second gap phase • M phase • Mitosis • Cytokinesis

  7. Eukaryoticcell cycle

  8. Structure of duplicated chromosome • Pair of sister chromatids • Contain identical DNA sequences • Tightly associated in region of centromeres • Each chromatid • Includes region called centromere • Kinetochore attached to each centromere

  9. Mitosis • Identical chromosomes distributed to each cell pole and a nuclear envelope forms • Stages • Prophase • Metaphase • Anaphase • Telophase

  10. Stages of Mitosis

  11. Asexual reproduction • Offspring have hereditary traits identical to single parent • Mitosis is basis • Sexual reproduction • Gametes fuse to form a zygote • Meiosis is basis

  12. Diploid cells • Characteristic number of chromosome pairs per cell • Homologous chromosomes • Similar in length, shape, other features, and carry similar attributes • Haploid cells • Contain only one member of each homologous chromosome pair

  13. Meiosis • Diploid cell undergoing meiosis yields four haploid cells

  14. Stages of Meiosis

  15. Meiosis in the trumpet lily

  16. Meiotic tetrad with two chiasmata

  17. Mitosis Prophase Anaphase Daughter cells Meiosis Prophase I Anaphase I Prophase II Anaphase II Haploid cells Mitosis vs. Meiosis

  18. Mitosis and meiosis

  19. Roles of mitosis and meiosis in various life cycles • Many simple eukaryotes remain haploid • In sexual life cycle, meiosis occurs before gametes form • Plants, some algae, and some fungi have complex life cycles with alternation of generations

  20. Representativelife cycles

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