Practice question

Prokaryotic genomes favor polycistronic transcription organization economizing regulatory DNA. Operon consists of promoter, operator, multiple adjacent structural genes encoding functionally related proteins transcribed into continuous messenger RNA carrying several ribosome binding sites. Translation can initiate independently at each cistron, often while transcription still progressing, allowing coupled transcription-translation. Examples include lactose, tryptophan, and arabinose operons. This strategy permits coordinated induction or repression via single regulator controlling whole pathway, contrasting with eukaryotic requirement for individual promoters for each gene due to nuclear processing and monocistronic export mechanisms.