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← Doubling

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Showing Revision 1 created 09/30/2013 by Cogi-Admin.

  1. If cells didn't double their DNA before dividing, then every
  2. time they divided they would cut their genome in half
  3. from 46 chromosomes to 23 in each daughter cell. All
  4. the chromes would line up in pairs and then separate in
  5. a way that each daughter cell would only get one
  6. of those chromosomes. Think about how bad this would be
  7. for trying to keep genetic consistency in all your cells.
  8. You'd have one mother cell here that's heterozygous for lactose metabolism.
  9. We have a dominant and a recessive allele, one
  10. on each chromosome. There's no duplication of DNA. So, after
  11. cell division occurs, then each daughter cell would only end
  12. up with one chromosome. And think about it, because of
  13. the heterozygous nature of the mother cell, each daughter cell
  14. is going to have a different genotype, a different genetic makeup.
  15. One will have the dominant allele for lactase persistence, and
  16. the other will have the recessive allele for lactase non-persistence.
  17. This would mean you'd have cells in your body
  18. that end up with different genotypes and different phenotypes.
  19. Therefore, before every cell division, the DNA would be
  20. duplicated. And that way, when cell division occurs, each
  21. daughter cell ends up with the same amount that
  22. the mother cell originally had before duplication. So just
  23. to make sure we're on the same page here.
  24. If DNA duplication does occur, how many chromosomes will
  25. each daughter cell have? Again, assume equal division,
  26. and put your numerical answer in this box here.