How were Spemann and Mangold able to tell that the organizer was directing cells of the host embryo to change their fates?
A - They assumed that all cells were dividing at the same rate and therefore some cells from the host embryo had to change their fate; otherwise there just wouldn't be enough cells.
B - They sequenced the DNA from different cells so that they could tell the host cells from the graft cells based on genotype.
C - They carefully observed the embryos differentiating under the microscope and kept track of which cells became what
D - They injected the graft cells with a dye to mark them and their progeny
E - The host cells and the graft cells had different pigmentation
Answer: E - The host cells and the graft cells had different pigmentation