Question: Consider a hypothetical strain of E. coli (strain 401) that contains a small deletion in the lead…

Consider a hypothetical strain of
E. coli (strain 401) that contains a small deletion in the
leader region of the trp operon. The deletion removes the
nucleotides encoding the ribosome binding site and initiation codon
for the leader peptide. See Figure 3 below.

Figure 3. The attenuator region of the Trp
operon. Regions 1-4 in the figure correspond to
sequences capable of forming the stem-loop structures shown in
Figure 10.15 A in the Slonczweski textbook (3^rd
edition).

Assume that strain 401 also contains
a mutation in the gene for the Trp aporepressor that abolishes its
ability to bind tryptophan and therefore cannot perform the
function of the Trp holorepressor. Answer the following questions
about how will the mutations in strain 401 will affect the
regulation of the trp operon. Specifically:

How will the events that are shown for the wild type
trp attenuator Fig 10.15 of the Slonczweski text differ in
the mutant?   Fill in the following table:

Wildtype

Mutant

Compare strain 401 with wildtype with respect to the expression
of the Trp operon under different culture conditions. Specifically:
how will the mutation affect the expression of the enzymes of the
trp operon when tryptophan is abundant and when it is
scarce?

Wildtype

Mutant

How would the mutation affect the mutant’s ability to grow in
rich media and minimal media? Fill in the tables below for both
wildtype E. coli and the mutant.

Wildtype

Mutant

Why would you not expect to see regulatory circuits such as the
trp attenuator in eucaryotic cells?