4. You are given an animal whose development has neverbeen characterized before. You note that at the four-cell stage,one blastomere transiently shows dark pigmentation. However, asembryogenesis proceeds, the dark pigmentation fades and you areunable to determine what becomes of the blastomere in thefully-developed embryo.
a) [4pts] Describe a simple experiment you can do todetermine the fate of the dark blastomere. Provide sufficientdetail to show that you understand the technique and itsinterpretation.
b) [5pts] For the animal described above, you find thatthe dark-pigmented blastomere at the four-cell stage ultimatelygives rise to all of the central nervous system of theembryo. Using this information, devise anexperiment to determine whether this cell is specified to be CNS atthe 4-cell stage. In addition to describing the experimentalprocedure, describe the possible results and how you wouldinterpret them.
c) [1pt] As this embryo undergoes gastrulation younotice that the ectodermal cells surround the endoderm similar toXenopus. What is the name to describe the movementof these ectodermal cells?
