Dimers formed by a normal protein will run through the gel-filtration column faster than a mutant protein Y monomer. Choice (b) is unlikely, because gel-filtration columns separate proteins on the basis of size, not charge or affinity for small molecules. Choice (c) is unlikely, because if the mutant protein were larger than normal it would be less able to enter the porous beads and would run through the column faster than the normal protein. Choice (d) is unlikely, because a small change in shape without a change in size
would be unlikely to have a major effect on the behavior of a protein in a gel-filtration column.
