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Meiosis

Meiosis. Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check with your neighbor). Egg cells in a female and Sperm cells in a male are both made by meiosis.

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Meiosis

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  1. Meiosis

  2. Meiosis is a process that reduces the amount of chromosomes in a cell to half the original amount Why would you want to reduce chromosomes to half? (check with your neighbor)

  3. Egg cells in a female and Sperm cells in a male are both made by meiosis Humans have 46 chromosomes in all of their cells except in egg and sperm cells/gametes/sex cells

  4. If meiosis reduces the chromosome number in half, how many chromosomes are in human sex cells? Egg = 23 Sperm = 23 Egg + Sperm = 46in them.

  5. Haploid (n)– a half set of chromosomes Diploid (2n) – a full set of chromosomes Somatic Cells = ALL body cells (blood, skin, etc) except gametes

  6. Haploid or Diploid? Gamete Skin Cell Egg Somatic Cell Sperm Sex Cell

  7. Homologous Chromosomes – chromosomes that have the same information Ex. Father/Paternal #11 chromosome Mother/Maternal #11 chromosome “Partner” up in Prophase 1

  8. Crossing Over is the exchange of genetic material between homologous chromosomes Crossing Overacts as a source of genetic variationwithin a species

  9. Stages of Meiosis • Interphase—1 time ONLY • Growth and replication of DNA • PMATC—2 times • Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

  10. Diploid Cell—2 copies of each chromosome that replicated during Interphase

  11. Crossing Over occurred during Prophase 1

  12. Anaphase AWAY

  13. Telophase I/Cytokinesis results in 2 Haploid Cells

  14. Prophase II looks similar to Telophase I, but nuclear envelope is disappearing again

  15. Anaphase Away—part II

  16. Telophase II and Cytokineses results in 4 HAPLOID sex cells….or gametes….or egg….or sperm!

  17. EggVsSperm Sperm Egg

  18. What’s different?

  19. Egg (Ovum) is created in the Ovary

  20. Sperm is created in the Testis

  21. Diploid Numbers in other Organisms

  22. Diploid Numbers in other Organisms

  23. Karyotype – a “map” of chromosomes • 2 Main Uses: • Determine sex of the baby • Screen for Chromosomal Abnormalities • Ex. Down Syndrome

  24. 22 pair of Autosomes + 1 pair of sex chromosomes = 23 Total pairs XX = Female XY = Male

  25. Male Karyotype

  26. Female Karyotype

  27. Sex Determination in Organisms Humans rely on Xs and Ys to determine if it’s a boy or girl, but what about other organisms? Do male ants have Fathers? Why are all turtles Hot Chics and Cool Dudes? Nemo’s dad Marlin should have been Marly?

  28. Questions about Meiosis????

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