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last updated by

pdavis68 18 years, 8 months ago

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- April 27, 2006 at 1:28 am #4617
  redfoxindigo
  Participant
  I’ve been working on this Unit for 3 weeks now and some of the questions they ask I just cannot find the answer to. I’ve been over 3 different text books and the internet and i’m just not finding them. Maybe I”ve already found the answer and just don’t know it, but do you think anyone could help?
  The questions I’m having trouble with are:
  1. What would probably happen if a small group of cells broke off of a human blastula?
  I’m thinking the answer is that you would get twins…am i right? I’ve searched but have not gotten any definit answers, but it seems like the most likely answer.
  2. Both egg and sperm cells donate 23 chromosomes to the zygote in human reproduction. What else is donated by the egg cell?
  If anyone can help me out here that would be great.
- April 27, 2006 at 1:37 am #47444
  mith
  Participant
  I believe mitochondria for #2
- April 27, 2006 at 3:21 pm #47494
  victor
  Participant
  I think your answer for #1 will occur when it’s in Morula stadium…
- April 29, 2006 at 12:22 pm #47603
  pdavis68
  Participant
  For #1, Identical twins will develop if a small group of cells breaks off within 4-12 days of fertizilization. If it happens after 12 days, you get conjoined twins.
  Fraternal twins result from two separate eggs being fertalized, so there’s no split in that case.
  The previous answer for #2 is correct as well. The sperm and egg contribute to the nuclear material but the egg alone contributes the mitochondria and mitochondria DNA.
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