Chapter 14, Problem 14CONQ

As shown in Figure 14.12, four regions within the trpL mRNA can form stem-loops. Let’s suppose that mutations have been previously identified that prevent the ability of a particular region to form a stem-loop with a complementary region. For example, a region 1 mutant cannot form a 1-2 stem-loop, but it can still form a 2-3 or 3-4 stem-loop. Likewise, a region 4 mutant can form a 1-2 or 2-3 stem-loop but not a 3-4 stem-loop. Under each of the following sets of conditions, would attenuation occur?

A. Region 1 is mutant, tryptophan is high, and translation is not occurring.

B. Region 2 is mutant, tryptophan is low, and translation is occurring.

C. Region 3 is mutant, tryptophan is high, and translation is not occurring.

D. Region 4 is mutant, tryptophan is low, and translation is not occurring.