Genetics: Analysis and Principles 4th Edition by Robert Brooker

Exercise 5

Mutations in bacterial promoters may increase or decrease the rate of gene transcription. Promoter mutations that increase transcription are termed up-promoter mutations, and those that decrease transcription are termed down-promoter mutations. As shown in Figure 12.5, the sequence of the 10 region of the promoter for the lac operon is TATGTT. Would you expect the following mutations to be up-promoter or down-promoter mutations
A. TATGTT to TATATT
B. TATGTT to TTTGTT
C. TATGTT to TATGAT
FIGURE 12.5 Examples of 35 and 10 sequences within several E. coli promoters. This figure shows the 35 and 10 sequences for one DNA strand found in seven different E. coli promoters. The consensus sequence is shown at the bottom. The spacer regions contain the designated number of nucleotides between the 35 and 10 region or between the 10 region and the transcriptional start site. For example, N 17 means there are 17 nucleotides between the end of the 35 region and the beginning of the 10 region.