Question

Which of the following gene is responsible for synthesis of a polypeptide chain that do not serve as regulatory protein?

• A. Promotor gene
• B. Structural gene
• C. Regulator gene
• D. Operator gene

Answer 1

The correct option is B Structural gene

• Promoter is a DNA segment that serves to initiate transcription of a particular gene. They are present upstream near the transcription start sites of genes.
• Regulator gene regulates the expression of structural genes by its protein product that are mostly transcription factors. These transcription factors bind to the operator region which is located just upstream the binding site of the RNA polymerase and hence, prevent the binding and transcription.
• Operator is a DNA sequence present between the promoter region and the first coding gene. This operator region serves as repressor protein binding site.
• The gene that codes for any RNA / protein product which do not serve as regulatory protein are known as structural genes. The lac Z, lac Y and lac A genes in lac operon are the structural genes.

So the correct answer is option B.