The fertilized egg must have enough cytoplasm to be able to divide repeatedly into the first few dozen cells of the embryo.
I think the kind of choices would be primary or secondary source: and this would be a secondary source:
a primary source would be the journals where the results were published and the secondary would be the tv program that used those reports as a primary report!
so the answer is secondary source!
I believe the stage of interphase in which cells copy their DNA is the S phase. :)
