You experimentally change the DNA sequence directly upstream of a start codon of an operon in E. coli to investigate the function of this region of DNA. Analysis reveals that after the change the same amount of mRNA is made from the operon, but there are very few proteins made from the operon. What is the most likely function of the DNA sequence that you changed?
A) The DNA sequence likely functions as a ribosome-binding site.
B) The DNA sequence likely functions as a promoter.
C) The DNA sequence likely functions as a termination sequence.
D) The DNA sequence likely functions as in transcriptional regulation.

Question

Quizplus · Accepted Answer

Since the same amount of mRNA is made from the operon but fewer proteins are made, it suggests that the mRNA is being degraded or the translation is being inhibited. The region directly upstream of the start codon is where the ribosome-binding site (RBS) is located. Therefore, it is likely that the DNA sequence change affects the RBS and reduces translation efficiency, leading to fewer proteins being made.

You Experimentally Change the DNA Sequence Directly Upstream of a Start