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Diploid vs. haploid

Diploid vs. haploid. chromosomes one copy of each = one set N; 2N N varies greatly from species to species N constant w/in species Humans: 2N = 46 Hermit crab: 2N = 256 Ascaris: 2N = 2 Ophioglossum reticulatum: 2N = 1,260 (actually, N = 15; 84N). Diploidy vs. haploidy.

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Diploid vs. haploid

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  1. Diploid vs. haploid • chromosomes • one copy of each = one set • N; 2N • N varies greatly from species to species • N constant w/in species • Humans: 2N = 46 • Hermit crab: 2N = 256 • Ascaris: 2N = 2 • Ophioglossum reticulatum: 2N = 1,260 (actually, N = 15; 84N)

  2. Diploidy vs. haploidy • Chromosomes … • Homologues • Maternal and paternal • genes, alleles, loci • genotype vs. phenotype • homozygote vs. heterozygote

  3. Homologues

  4. Genotype: AA Bb cc Phenotype: ABc

  5. Diploidy vs. haploidy ... • Chromosomes … • morphology • karyotypes • prior to cell division • duplicated chromosomes - chromatids • centromere placement • metacentric, acrocentric, telocentric • telomeres • banding patterns

  6. Mitosis vs. Meiosis • Mitosis leads to growth, somatic cells (usually) • one cell forms two cells • 2N  2N (1N  1N) • daughter cells are identical • Meiosis leads to gametes (usually) • one cell forms four cells • 2N  N • two divisions • daughter cells are not identical

  7. Cell Cycle • G1 • growth, cell performing its function • S • synthesis of DNA • G2 • continued growth, cell metabolizing • Division (mitosis or meiosis)

  8. Mitosis • 5 Stages • Interphase (G1-S-G2) • Prophase • condensation of chromosomes • breakdown of nuclear membrane • centrosome duplicates, move to opposite poles • spindle fibers begin to form

  9. Interphase --> Prophase Single chromosomes Duplicated chromosomes (not visible) (chromatids) (visible)

  10. Mitosis ... • Metaphase • nuclear membrane gone • centrioles at opposite poles • spindle fibers attached to centromeres and centrosomes • chromosomes move to cell equator - “metaphase plate”

  11. Metaphase centrisome metaphase plate

  12. Mitosis ... • Anaphase • spindle fibers shorten, pulling chromatids apart - “disjunction” • chromatids separate, move to opposite poles

  13. Anaphase

  14. Mitosis • Telophase • chromosomes relax • nuclear membrane reforms • plants: cell wall; animals: cell furrow • cytokinesis complete

  15. Telophase

  16. Mitosis in a diploid cell

  17. Mitosis in a haploid cell

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