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← Arms Race

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Showing Revision 1 created 09/29/2013 by Cogi-Admin.

  1. What would happen if a germ cell went through
  2. mitosis? Now think about it for a second. Mitosis
  3. results in two cells that have the same number
  4. of chromosomes that the parent cell had, 46 chromosomes.
  5. This means that the germ cell would be making
  6. two gametes each with 46 chromosomes. If a sperm
  7. with 46 chromosomes fertilizes an egg that also has
  8. 46 chromosomes, then that would result in a cell with
  9. 92 chromosomes. That's twice as much as human
  10. cells are supposed to have. If we take this
  11. to its logical conclusion, while the first humans
  12. would have 46 chromosomes, the next generation would have
  13. 92 and the next generation would have 184.
  14. And the next generation would have 368, and so
  15. forth and so on. We would just be in
  16. this endless arms race, doubling our chromosomes every generation.
  17. So this, just doesn't work. Germ cells go
  18. through a very special kind of division, called meiosis.
  19. And this division is different from every other cell
  20. type in your body. And the reason is specifically,
  21. to solve this problem of having too many chromosomes
  22. at fertilization. What happens is DNAs duplicated just like
  23. in mitosis, but then there's a round of cell
  24. division. And then the resulting cells, without duplicating their
  25. DNA again, go through another round of cell division and in this case we
  26. separate out. Every chromosome now, is not in a pair. The
  27. pairs have been broken up. How many chromosomes would a gamete have
  28. after meiosis? Go ahead and put your, numerical answer in this box here.