You are analyzing an unknown gene that is expressed robustly

You are analyzing an unknown gene that is expressed robustly under certain conditions. You have sequenced the gene and in the 5\' UTR of the mRNA you find the following sequence: 5\'-CGCCGCCGCCGCCGC-3\'. You cleverly use a process called \"site-directed mutagenesis\" to change the sequence to 5\'-AGAAGAAGAAGAAGA-3\' Now, expression of the gene controlled by this 5\' UTR is very poor in response to the signal.

1) What could be causing this?

Solution

Site directed mutagenesis changes Cysteine to adenine. The specific and unique sequences for an activator to bind to the mRNA and initiate transcription of this partiular protein is this UTR site. When this UTR is modified the activator cannot bind to this region and cannot activate transcription of that particular protein. Hence the protein or the gene is not expressed when site directed mutagenesis of cysteine to adenine. Hence poor signal .