Essential Genetics 6th Edition by Daniel Hartl

Exercise 3

Imagine a bacterial species in which the methionine operon is regulated only by an attenuator and there is no repressor. In its mode of operation, the methionine attenuator is exactly analogous to the trp attenuator of E. coli. The relevant portion of the attenuator sequence in the RNA is

The translation start site is located upstream from this sequence, and the region shown is in the correct reading frame. What phenotype (constitutive, wildtype, or
would you expect for each of the types of mutant RNA below? Explain your reasoning.
(a) The red A is deleted.
(b) Both the red A and the underlined A are deleted.
(c) The first three As in the sequence are deleted.