Question

function. loss-of-function mutations prevent signaling in gpcr pathways, even in the presence of signaling molecules. gain-of-function mutations activate signaling in gpcr pathways, even in the absence of signaling molecules.

which of the following will most likely be found in an individual with a gain-of-function gpcr mutation?

choose 1 answer:

a signal transduction pathways that are activated even if ligand-to-receptor binding does not occur

b signal transduction pathways that are inactive if ligand-to-receptor binding does not occur

c signal transduction pathways that are activated only if ligand-to-receptor binding occurs

d signal transduction pathways that are inactive even if ligand-to-receptor binding occurs

Explanation:

The question is about GPCR (G - protein - coupled receptor) mutations. A gain - of - function mutation in GPCR activates signaling in GPCR pathways even in the absence of signaling molecules (ligands). Ligand - to - receptor binding is the normal way to activate the signal transduction pathway. So with a gain - of - function mutation, the signal transduction pathway can be activated without ligand - to - receptor binding.

• Option A: Matches the description of gain - of - function mutation as it says signal transduction pathways are activated even without ligand - to - receptor binding.
• Option B: Says the pathway is inactive without ligand binding, which is the normal situation, not gain - of - function.
• Option C: Says activation only if ligand binding occurs, which is normal, not gain - of - function.
• Option D: Says inactive even with ligand binding, which is loss - of - function, not gain - of - function.

Answer:

A. Signal transduction pathways that are activated even if ligand - to - receptor binding does not occur