Final answer:
A mutation in the operator sequence of the trp operon that prevents the repressor protein from binding to the operator would cause the amount of attenuation to be reduced in the mutant.
Step-by-step explanation:
A type of mutation in the Trp gene that would cause the amount of attenuation to be reduced in the mutant is a mutation in the operator sequence of the trp operon that prevents the repressor protein from binding to the operator. The repressor protein normally binds to the operator, preventing RNA polymerase from transcribing the genes involved in tryptophan synthesis. Without the repressor protein binding, the genes will be transcribed even in the presence of tryptophan, reducing the level of attenuation.