Genna is describing an experimental result in which a metabotropic receptor activated multiple proteins. Genna is describing a(n):

Amplification cascade

Explanation:

Amplification cascade also known as Signaling pathway occurs when a stimulus or first messenger prompts a biological reaction within a cell which in turn acts on a receptor that undergoes signal transduction and amplification caused by secondary messengers. These secondary messengers send the signal to the effector sites who now produce a response to the initial stimuli.

So, the basic principle of an amplification cascade is the fact that a particular action triggers the response of several other factors. This is similar to what Genna describes in her experiment where a metabotropic receptor activated multiple proteins.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.