3.The tiny invertebrate Hydra has an apical region with tentacles and a long, slender body. Hydra can reproduce asexually when cells on the body wall differentiate and form a bud, which then breaks off as a new organism. Buds form only at certain distances from the apex, leading to the idea that the apex releases a signal molecule that diffuses down the body and, at high concentrations (i.e., near the apex), inhibits bud formation. Hydra lacks a circulatory system, so this inhibitor must diffuse from cell to cell. If you have an antibody that binds to connexons and plugs up the gap junctions, how would you test the hypothesis that Hydra’s inhibitory factor passes through these junctions?
Experiments might involve applying a solution containing the antibody to the upper part of the Hydra body. The antibody would block diffusion of the signal molecule from the apex to the upper body and—if the hypothesis is correct—would allow a bud to form in the upper body. A sham experiment, in which the solution without antibody is applied, would be a control. In this case, a bud would not form in the upper body.