Practice Questions

TLS Online TPP Program

#Question id: 15658

You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium.
Next, you isolate a third mutant, MelC–, which gives constitutive melibiase expression. The MelC– mutation is closely linked to Mel1 and MelB–. Genetic tests of the MelC– mutation yield the following:

As above, classify the MelC– mutation in terms of its basic genetic properties and explain how you arrived at your conclusions.

#SCPH06 I Botany

MelC- being neither a dominant negative mutation in a negative regulator (repressor-d) or a super activator mutation (activators⁵).
MelC- being only a super activator mutation (activators⁵).
MelC- being only a dominant negative mutation in a negative regulator (repressor^-d)
MelC- being either a dominant negative mutation in a negative regulator (repressor^-d) or a super activator mutation (activators⁵).