1 / 23

Meiosis

Meiosis. Meiosis Overview. Meiosis - cell division in which gametes are made (eggs and sperm). The cells made will have half the number of chromosomes of the parent cell. Homologous – chromosomes with a corresponding partner. (one from mom & one from Dad).

fletcher-hampton
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. Meiosis Overview • Meiosis - cell division in which gametes are made (eggs and sperm). The cells made will have half the number of chromosomes of the parent cell. • Homologous – chromosomes with a corresponding partner. (one from mom & one from Dad)

  3. Haploid – a cell that contains only one of each homologous chromosome pair; half the total.(sperm, egg) • Diploid – a cell that contains both homologous chromosomes; full set.(body cells)

  4. Meiosis I

  5. Nucleus Interphase I • Cell starts out as a DIPLOID cell. Either a SPERMATOCYTE or an OOCYTE • Chromatin replicates. Cell Membrane

  6. Prophase I • Nucleus starts to disappear. • Sister Chromatids pair up to form chromosomes, which now can be seen. • Homologous Chromosomes pair up to form tetrads, • (2 homologs together). • 4. Centrioles move to the poles • 5. Crossing-over can occur during the latter part of this stage.

  7. Crossing Over • Crossing over: the swapping of DNA which occurs between homologs. • It gives us genetic variation or differences. • This is one reason why you are your own unique person.

  8. Spindle Fibers Metaphase I • Spindle Fibers appear. • Tetrads line up along the middle of the spindle. • Fibers attach to centromeres.

  9. Anaphase I • Spindle fibers pull the tetrads apart, with sister chromatids remaining together. • 2. Chromosomes are pulled to the centrioles.

  10. Telophase I • Spindle Fibers and centrioles disappear. • Nucleus reappears around each of the new sets of chromosomes. • Cell starts to form a break at the middle and starts to pinch in at the sides.

  11. Telophase I (continued) • Cytokinesis occurs

  12. Meiosis II Continues with both cells, but this will only show one Movie

  13. Prophase II 1. Chromosomes are already visible 2. Nucleus disappears 3. Centrioles move to the poles

  14. Metaphase II 1. Spindle Fibers appear 2. Chromosomes are lined up along middle of cell

  15. Anaphase II • Spindle fibers pull sister chromatids to each pole.

  16. Telophase II 1. Spindle fibers and centrioles disappear 2. A nucleus appears around each set of chromosomes 3. Cell starts to pinch in at the center

  17. Telophase II (Continued) 1. Both cells divide (cytokinesis), leaving 4 new cells 2. Each with half the number of chromosomes the original cell had. 3. Each cell is now HAPLOID, called a gamete. 4. Gametes can be sperms or eggs.

  18. Spermatogenesis- making sperm cells by meiosis. Makes 4 sperm

  19. Oogenesis - making egg cells by meiosis. Makes 1 egg and 3 polar bodies Movie

  20. Comparing Mitosis and Meiosis Mitosis • Happens all over body • IPMAT • Makes 2 cells • Diploid cells—full set of chromosomes • Make new body cells • 1 set of divisions

  21. Comparing Mitosis and Meiosis Meiosis • Reproductive organs • IPMAT - PMAT • Makes 4 cells • Haploid—1/2 set of chromosomes • Makes sex cells (Gametes) • 2 sets of divisions • Crossing over

  22. Mitosis and Meiosis • Mitosis allows for genetic continuity within an organism. • Meiosis allows genetic variety during sexual reproduction.

More Related