You are investigating a newly discovered operon in bacteria

You are investigating a newly discovered operon in bacteria. This operon has two genes that are regulated together under the control of a single promoter and a single transcription factor. There are five regions: A regulatory gene for the transcription factor protein A promoter for the structural genes in the operon A binding site for the transcription factor A structural gene for an enzyme (Gene 1) A structural gene for a channel protein (Gene 2) Expression of the wild-type operon is dependent on an external signal, namely the presence or absence of an amino acid. To determine the function of different regions of this segment of DNA, you make mutations and determine the effect on protein production in the presence and absence of the signal. The results are shown in the table. A plus sign (+) indicates that a functional protein is made; a minus sign (-) indicates that no functional protein is made. What is the identity of region C? Select all possible options. A. A regulatory gene for the transcription factor protein B. Promoter for the structural genes in the operon C. Binding site for the transcription factor D. A structural gene for an enzyme (Gene 1) E. A structural gene for a channel protein (Gene 2)

Solution

Under region C, + sign indicating a functional protein has been made. Region D also showing + sign indicating a functional protein has been made. Repressor is active, repressor bound to operator in the absence of lactose. The region c ia a promoter and d is operator. The region c is a regulatory gene, lacI. The lacI, produces lac repressor protein which binds to regulate operon. Correct option is..............A. A regulatory gene for the transcription factor protein