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Chapter 13 Meiosis

Chapter 13 Meiosis. Chapter 13 Meiosis. Terms Heredity Transmission of traits to offspring Variation Genetic variation in population Genetics Study of heredity Genes DNA coded information for protein Gametes Sperm and egg (and spores). sexual reproduction.

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Chapter 13 Meiosis

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  1. Chapter 13 Meiosis

  2. Chapter 13 Meiosis • Terms • Heredity • Transmission of traits to offspring • Variation • Genetic variation in population • Genetics • Study of heredity • Genes • DNA coded information for protein • Gametes • Sperm and egg (and spores)

  3. sexual reproduction • 2 parents give rise to genetically unique offspring

  4. Sexual Life Cycles • Life cycle – from conception to production of offspring

  5. Some organisms can also reproduce asexually Sea sponge fragmentation Paramecium binary fission Sea star regeneration ginger rhizome yeast budding

  6. Komodo dragon parthenogenesis

  7. Other animals and plants reproduce sexually Male sea star releasing sperm into water, some sea stars are hermaphrodites and release both sperm and egg

  8. Germ line cells (gametes) 1n (haploid) Fertilization1n + 1n = 2n (diploid)

  9. Sperm + egg--- zygote fertilization • A dog fertilized egg has 78 chromosomes • # in a dog sperm • # in a puppy’s brain cell • # in a dog embryo cell Haploid  diploid  haploid  diploid etc………….

  10. Human chromosomes

  11. Arranged in homologous pairs Autosomes = pairs 1 – 22 Sex chromosomes = pair 23 XX = female XY = male

  12. Germ line cells (gametes)– ovary/testes • 1n (haploid) = 23 Fertilization 1n + 1n = 2n Ex. Fruit fly egg has 4 chromosomes (1n). How many chromosomes in a sperm? A fly larval cell? An adult somatic cell?

  13. Sperm + egg--- zygote fertilization Haploid  diploid  haploid  diploid etc………….

  14. Humans: 2n = n =what makes chromosomes homologous? Homologous chromosomes Same length Same genes at same locations

  15. When meiosis is complete: 4 new haploid cells genetically unique

  16. Interphase • Same as in mitosis! • Sister chromatids identical

  17. Stages of Meiosis Prophase I Same as mitosis except………………> 2n = ? The number of pairs of homologous chromosomes is?

  18. Prophase I Synapsis replicated homologous chromosomes form a tetrad What is happening here?

  19. 2n = sister chromatid pairs = total sister chromatids =tetrads =

  20. Which is prophase of mitosis? Prophase I of meiosis? No synapsis between homologous chromosomes Synapsis

  21. Crossing over • Non -sister chromatids exchange • Creates diversity!

  22. Prophase I • Crossing over – note chiasma What is this structure? • How many sister chromatids participate in each tetrad?

  23. Metaphase I • Tetrads line up along metaphase plate

  24. Which is metaphase of mitosis? Metaphase I of meiosis? Test your knowledge. How many tetrads in a human ovarian cell in metaphase I of meiosis?

  25. Anaphase I Homologs separate and move towards opposite poles Note: sister chromatids still connected

  26. Which is anaphase of mitosis?

  27. Telophase I • Nuclear membranes form  cytokinesis • 2 haploid daughter cells Why are these haploid?

  28. Overview of Meiosis 1 • Bioflix meiosis animation • Bioflix on youtube • Meiosis I is =reduction division • Each cell has 1 set of chromosomes (replicated and recombined)

  29. Meiosis II • Prophase II

  30. Metaphase II

  31. Anaphase II

  32. Telophase II  4 genetically unique haploid cells

  33. Meiosis and genetic variation 1. crossing over (prophase I)  recombinant chromosomes 2. independent assortment random orientation of homologous chromosomes are metaphase I

  34. 3. random fertilization Humans: 223 X 223 =

  35. Compare mitosis and meiosis

  36. Overview of Meiosis Activities quiz

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