A mutation in a G-protein prevents the alpha-subunit from dissociating from the beta/gamma-subunit. What effect will this have on the pathway in which the G-protein is involved?

the pathway will be under-expressed.

if G-protein Coupled Receptor is unable from dissociating β and γ subunits, then the pathway will go under expression.  

The chemical qualities of the alpha subunit allow it to bind easily to one of two guanine subunits, GDP or GTP. The protein thus has two functional formations. When GDP is bound to the alpha subunit, the alpha subunit remains bound to the beta-gamma subunit to form an inactive trimeric protein.

G-proteins, cAMP, and Ion Channel Opening. The alpha subunit activates adenylate cyclase, in purple, and loses GTP. Adenylate cyclase converts ATP to cyclic AMP, which then activates Protein Kinase, shown in blue. Protein Kinase phosphorylates an ion channel, letting sodium ions rush into the cell.

As a result of the ligand binding to its site on the G-protein-linked receptor, A) the G-protein changes conformation and GTP replaces the GDP on the alpha subunit. ... Inactivation of the alpha subunit occurs when its own phosphorylase activity removes a phosphate from the GTP.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!