They typically produce a single polycistronic mRNA, and one of these sequences known as araBAD controls arabinose metabolism. The Z, Y, and A genes in one of these sequences code for permease, transacetylase, and beta-galactosidease. Tetrameric protein repressors can prevent RNA polymerase from binding to these (*) gene sequences, and they can produce enzymes that synthesize tryptophan and metabolize lactose. For 10 points, name these regulatory systems in bacteria and viruses, series of structural genes that are controlled by a promoter, like 
They typically produce a single polycistronic mRNA, and one of these sequences known as araBAD controls arabinose metabolism. The Z, Y, and A genes in one of these sequences code for permease, transacetylase, and beta-galactosidease. Tetrameric protein repressors can prevent RNA polymerase from binding to these (*) gene sequences, and they can produce enzymes that synthesize tryptophan and metabolize lactose. For 10 points, name these regulatory systems in bacteria and viruses, series of structural genes that are controlled by a promoter, like the lac one.
They typically produce a single polycistronic mRNA, and one of these sequences known as araBAD controls arabinose metabolism.