4. You are given an animal whose development has never been characterized before. You note that...

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Biology

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?

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3.7 Ratings (538 Votes)

a the gray crescent is the area that determines the secondaryaxis This is the dark blastomere at the four celled stage Spemanconducted experiments with this gray crescent to determine its fateand rolethe Spemann experiment is given belowHe constricted the embryo in a way that the grey crescent isequally divided between two halves This See Answer

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