Based on the results, which conclusion is correct? A. In sea urchins, only the fate of the ectodermal cells is conserved. B. In sea urchins, only the fate of the endodermal cells is conserved. C. In sea urchins, the fate of the ectodermal and mesodermal cells is conserved. D. In sea urchins, the fate of the three gem layers is conserved between the two clades.
Fluorescence Mapping of Blastomere in Sea Urchins
Fate mapping is a technique that allows determination of the fate of cells from the three germ layers. In worms, the endoderm gives rise to the cells that line the intestines. The ectoderm gives rise to cells of the nervous system and body covering. The mesoderm gives rise to the muscles and other organs between the ectoderm and mesoderm. A researcher is tracing the fate of a particular cell (blastomere) from its position in one of the three germ layers of sea urchin blastulae by injecting a fluorescent tag in cells of the ectoderm, mesoderm, and endoderm. Several weeks later, the sea urchin embryos were analyzed for the presence of fluorescence in specific tissues. The following results were obtained.
| Tissue | Percent increase fluorescence over background when dye is injected in the ectoderm | Percent increase fluorescence over background when dye is injected in the mesoderm | Percent increase fluorescence over background when dye is injected in the endoderm |
| Nerve ring | 40% | 5% | 3% |
| Intestinal lining | 8% | 6% | 70% |
| Nerve cords | 59% | 6% | 7% |
| Water vascular system | 7% | 40 | 40% |
| Tube feet | 10% | 60% | 9% |
| Epidermis covering endoskeleton | 47% | 8% | 6% |
Use the passage to answer the question.
Based on the results, which conclusion is correct?
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A.
In sea urchins, only the fate of the ectodermal cells is conserved.
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B.
In sea urchins, only the fate of the endodermal cells is conserved.
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C.
In sea urchins, the fate of the ectodermal and mesodermal cells is conserved.
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D.
In sea urchins, the fate of the three gem layers is conserved between the two clades.
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