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Do-Now: Review from Mitosis

Do-Now: Review from Mitosis. A human body cell has 46 chromosomes. In a human body cell, mitosis produces A) two cells with 46 chromosomes in each. B) two cells with 23 chromosomes in each. C) four cells with 23 chromosomes in each. D) four cells with 46 chromosomes in each.

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Do-Now: Review from Mitosis

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  1. Do-Now: Review from Mitosis • A human body cell has 46 chromosomes. In a human body cell, mitosis produces A) two cells with 46 chromosomes in each. B) two cells with 23 chromosomes in each. C) four cells with 23 chromosomes in each. D) four cells with 46 chromosomes in each.

  2. Do-Now: Review from Mitosis • A human body cell has 46 chromosomes. In a human body cell, mitosis produces A) two cells with 46 chromosomes in each. B) two cells with 23 chromosomes in each. C) four cells with 23 chromosomes in each. D) four cells with 46 chromosomes in each.

  3. Mitosis Review • In mitosis, a parent body cell divides to make two daughter body cells • New daughter cells are diploid…have two sets of chromosomes (46 total in humans) • Example: one blood cell divides to make two blood cells

  4. Mitosis Review Only DIPLOID cells are made in mitosis

  5. During meiosis, new SEX CELLS (eggs and sperm) are created. • 2) Eggs and sperm are haploid, meaning they have one set of chromosomes (23 total). Meiosis- A New Type of Division Why might it be a problem for sex cells to be diploid ?

  6. Meiosis • A process where the nucleus divides that splits the original chromosomes into haploid daughter cells Human Body Cell = 46 Egg or Sperm Cell = 23 • Why?... so that chromosome number won’t be doubled during fertilization • Key Point: Meiosis makes fertilization possible!!!

  7. Types of Reproduction • Asexual = makes offspring (children) that are identical to the parent (ex: binary fission in bacteria or “budding” in sponges) 2. Sexual = makes offspring that are different from the parent, meiosis happens and then sperm and egg join

  8. Stages • Before meiosis begins: Interphase (G1, S, G2) • What happens during each part of interphase? Is this considered part of cell division? • During Meiosis: -Meiosis I -Meisis II

  9. Remember the Cell Cycle? Meiosis uses the same cycle as mitosis, except meiosis happens in 2 parts. Interphase must still happen so the cell can grow, copy its DNA, and prepare for division.

  10. Meiosis I • Chromosome number gets cut in half (1 diploid cell  2 haploid cells) • 4 parts 1) Prophase I 2) Metaphase I 3) Anaphase I 4) Telophase I

  11. Prophase I Similarities to Mitosis: • DNA coils into chromosomes • Spindle fibers are made • Nuclear Membrane breaks down

  12. Prophase I • Differences from Mitosis • Homologous chromosomes pair up • Homologous chromosomes = pairs of chromosomes (1 from mother and 1 from father) that have the same genes (ex: gene for eye color)

  13. Prophase I: Crossing Over • Crossing over = homologous chromosomes “trade” genes • Results in Genetic Recombination • Tetrad =the pair of chromosomes

  14. Why does crossing over take place? • Trades genes so that offspring look different from either parent and from their siblings.

  15. Prophase I Label: • Homologous Chromosomes • Nuclear Membrane • Spindle • Crossing Over

  16. Metaphase I • Tetrads line up in the middle of the cell • Spindle fibers attach to the chromosomes Label: Homologous Chromosomes, Centromere, Spindle, Metaphase Plate

  17. Anaphase I • Homologous Chromosomes move to opposite ends of the cell Label: Homologous chromosomes, spindle

  18. Telophase I and Cytokinesis • Chromosomes reach opposite ends • Cytoplasm divides • End Result = 2 daughter cells with half the original chromosome number Label: Nuclear membrane, centrioles, chromosomes

  19. Meiosis II • DNA is NOT copied again • Chromatids (identical copies of DNA) separate like they do during mitosis • 4 Stages: 1) Prophase II 2) Metaphase II 3) Anaphase II 4) Telophase II and Cytokinesis

  20. Meiosis II End Result of Meiosis: 4 haploid daughter cells

  21. Prophase II • Nuclear membrane breaks down • Spindle is made Label: Nuclear membrane, spindle, chromosomes

  22. Metaphase II • Spindle fibers move chromosomes to the center of the cell Label: Chromosomes, Chromatids, Centromere, Spindle, Metaphase Plate

  23. Anaphase II • Chromatids of each chromosome separate at the centromere and move toward opposite ends of the cell Label: New Chromosomes, Spindle

  24. Telophase II and Cytokinesis • Spindle breaks down • Chromosomes uncoil Nuclearenvelopes form • Cytoplasm divides Label: Nuclear Membrane, Centrioles, Uncoiling Chromosomes (chromatin)

  25. Main Goal: Making Sex Cells! • Gametes = haploid reproductive cells made during meiosis (ex: sperm and egg) • Sex cells are made in the testes and ovariesin humans

  26. Spermatogenesis • The process of making sperm cells • Diploid cell divides by meiosis to form four haploid sperm cells

  27. Spermatogenesis

  28. Oogenesis • The process of making egg cells • A diploid cell divides by meiosis to make ONE mature egg cell • Other three haploid cells = polar bodies

  29. Oogenesis • Egg gets all the cytoplasm and organelles, polar bodies are tiny little structures with DNA only • Polar bodies break down and die 

  30. Warm Up • What does it mean to be a diploid cell? • How does meiosis make fertilization possible? • What are three ways in which asexual reproduction is different from sexual reproduction? • Is Interphase considered part of cell division? • How does crossing over contribute to genetic variability? • How is the end result of meiosis different from the end result of mitosis? • How is the one egg cell different from the three polar bodies? • What is the main difference between spermatogenesis and oogenesis? • How is Prophase 1 of meiosis and Prophase of mitosis different? • Which part of meiosis (meiosis 1 or meiosis 2) is most like mitosis?

  31. Meiosis Poster: 8 Section, Label Phases, Draw Diagrams, Describe what is Going on at each phase, Label. Use COLOR. Follow Chromosomes. Prophase 1 Label: Homologous Chromosomes, Centrioles, Nuclear Membrane, Sister Chromatids, Spindle Fibers, Tetrad, Crossing Over Metaphase 1 Label: Homologous Chromosomes, Centrioles, Centromere, Spindle Fibers, Metaphase Plate, Sister Chromatids Anaphase 1 Label: Homologous Chromosomes, Centrioles, Sister Chromatids, Spindle Fibers Telophase 1 Label: Nuclear membrane, Centrioles, Spindle Fibers, Homologous Chromosomes, Sister Chromatids Prophase 2 Label: Nuclear membrane, Spindle Fibers, Centriole, Homologous Chromosomes, Sister Chromatids Metaphase 2 Label: Homologous Chromosomes, Sister Chromatids, Centromere, Spindle Fibers, Centrioles, Metaphase Plate Anaphase 2 Label: Nuclear Membrane, Centrioles, Sister Chromatids, Spindle Fibers Telophase 2 Label: Nuclear Membrane, Centrioles, Uncoiling Sister Chromatids (chromatin), Spindle Fibers Don’t Forget to Label Diploid and Haploid

  32. On a separate sheet of paper compare/contrast Mitosis and Meiosis (I can come up with at least 15. . . . How about you?) DUE Wednesday!! Have a WONDERFUL Break 

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