Essential Genetics 6th Edition by Daniel Hartl

Exercise 19

In yeast, transcription of the GAL (galactose-utilization) genes is regulated by the GAL4 protein (designated GAL4p), which promotes transcription by recruiting the transcription complex to the promoter. In the absence of galactose, GAL3p binds to GAL80p and sequesters it in the cytoplasm. In the presence of galactose, the galactose binds with GAL3p and triggers the release of GAL80p.
(a) Would a mutant GAL4p that prevents it from interacting with the transcription complex (but does not interfere with its other functions) be inducible, noninducible, or constitutive? Would the mutation be dominant or recessive to the wildtype allele?
(b) Would a mutation in GAL80p that prevents it from interacting with GAL4p (but does not interfere with its other functions) be inducible, noninducible, or constitutive? Would the mutation be dominant or recessive to the wildtype allele?