Most structural genes of bacteria are grouped together and transcribed from a single ___; immediately following this sequence is the that interacts with a regulatory protein to affect transcription of the genes. A. gene; promoter B. ribosome; promoter C. promoter; operator D. promoter; structural gene E. regulon; operon

Related genes in bacteria are often found in a cluster on the chromosome, where they are transcribed from one RNA polymerase binding site(promoter) as a single unit while other regulatory proteins are binding repressors attached to DNA pieces known as operators. When they are bound to operator, a repressor reduces transcription.

Genes in cases like this encode proteins, having various roles which include fuel metabolism, maintenance of cell structure, and

also defense against viruses in its process. A great number of these proteins are been used while others are needed only under certain decrees. Therefore, it is said that cells don't express all the genes in their genome always.