Genetics: Analysis and Principles 4th Edition by Robert Brooker

Exercise 16

As described in Figure 14.14, four regions within the trpL gene can form stem-loop structures. Let's suppose that mutations have been previously identified that prevent the ability of a particular region to form a stem-loop structure with a complementary region. For example, a region 1 mutant cannot form a 1-2 stem-loop structure, but it can still form a 2-3 or 3-4 structure. Likewise, a region 4 mutant can form a 1-2 or 2-3 stem-loop but not a 3-4 stem-loop. Under the following 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.