1 / 33

MEIOSIS

MEIOSIS. Review:. Homologous Chromosomes: matching pair of chromosomes, one inherited from each parent. Review. “Somatic”: body cells, non sex cells, they are diploid “Diploid” or 2N: having two sets of chromosomes “Haploid” or N: having one set of chromosomes.

enya
Download Presentation

MEIOSIS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MEIOSIS

  2. Review: Homologous Chromosomes: matching pair of chromosomes, one inherited from each parent

  3. Review • “Somatic”: body cells, non sex cells, they are diploid • “Diploid” or 2N: having two sets of chromosomes • “Haploid” or N: having one set of chromosomes

  4. Diploid vs. Haploid Exercises • Drosophilia have a diploid number of 8. What is the haploid? • Onions have a haploid number of 8. What is the 2N? • A horse’s 2N is 64. What is the 1N? • A body cell of an alligator has 32 chromosomes. Is this the diploid or haploid number? 4 16 32 Diploid

  5. II. Meiosis • Definition: cell division to produce egg (ovule) or sperm (pollen)

  6. Karyotypes • Display of chromosomes lined up in homologous pairs • Half inherited from male Half from female • Used for viewing #, size, shape, and banding • patterns of chromosomes

  7. Autosomes [#1-22] Chromosomes that are not sex chromosomes • Sex chromosomes [#23] Mammal females: XX Mammal males: Xy

  8. Fertilization: when haploid sperm and egg meet, combining N chromosomes with N chromosomes = 2N zygote • Zygote: fertilized egg, 2N 23 23 46

  9. General Process of Meiosis • MEIOSIS I (PMAT I &C) - Prophase I: homologous chromosomes meet up and form tetrads. Crossing over occurs. - Metaphase I: homologous chromosomes line up along the equator; the assortment among homologs is random

  10. Process of Meiosis Con.’t - Anaphase I and Telophase I occur as usual - Cytokinesis splits cell in half. - Begins with one 2N gametocyte - Ends with two 1N cells

  11. INDEPENDENT ASSORTMENT

  12. CELL THEN GOES THROUGH “INTERKINESIS”- NO MORE DOUBLING OF CHROMOSOMES!!

  13. General Process of Meiosis • MEIOSIS II (PMAT II & C) - Starts with 2 haploid cells - Prophase, Metaphase, Anaphase, Telophase II and Cytokinesis serve to separate the sister chromatids - Ending Cells: 4 cells, each with haploid chromosomes

  14. Another Animation of Overall Meiosis

  15. Oogenesis: Production of Egg • Female meiosis in the ovaries • Resulting cells: 1 egg, 3 polar bodies • Haploid

  16. Spermatogenesis:Production of Sperm • Male meiosis in testes • Resulting cells: 4 haploid sperm cells

  17. Comparison between Spermatogenesis and Oogenesis

  18. What if Meiosis Did Not Use Haploid Cells? Every generation would inherit twice as many chromosomes: • Sperm (23) + Egg (23) = 46 chromosomes • Sperm (46) + Egg (46) = 92 chromosomes • Sperm (92) + Egg (92) = 184 chromosomes…

  19. Mitosis Cell division 46 chromo2 cells, 46 chromo. Each Keeps chromo. # same Found in body cells Most common No genetic variation Meiosis Cell division 46 chromo 4 cells, 23 chromo each Chromo. # cut in half Found in sex/germ cells ONLY Least common Most genetic variation ANIMATION OF COMPARISON ANIMATION 2 OF COMPARISON

More Related