Solutions For An Introduction to Genetic Analysis Chapter 12 Problem 35P

A mutation in TFC would restrain the complex being formed by TFA, TFB, and TFC respectively, as a result of the change in the interaction sites. It is the interaction site that has a major effect on the formation of complex than the whole complex itself.

Hence, if there is mutation at the interaction site, there would not be any interaction among the transcription factors, thus restricting transcription.