[Campbell Biology P.1111] The "WHAT IF?" section asks how injecting a protein candidate into ... | Practice Question

The "WHAT IF?" section asks how injecting a protein candidate into ventral cells of a gastrula would test its function as a signaling molecule from the dorsal lip. What outcome would best support the candidate protein's role as the dorsal lip's signaling molecule?

  • A: The injected cells, or surrounding ventral cells, are induced to form dorsal structures such as a notochord and neural tube, potentially leading to a partial secondary axis.
  • B: The gastrula undergoes apoptosis, indicating the protein is toxic.
  • C: The entire gastrula transforms into a fully developed limb bud.
  • D: No observable change occurs, indicating the protein is not functional in vivo.

Explanation

The "WHAT IF?" question proposes a test for a signaling molecule from the dorsal lip. The dorsal lip's function as an organizer is to induce surrounding ventral tissues to form dorsal structures, essentially creating a secondary embryonic axis. Therefore, if the candidate protein is indeed the signaling molecule, injecting it into ventral cells should mimic this inductive effect, leading to the formation of dorsal structures like the notochord and neural tube in the ventral region.