Transcripts are polycistronic.

• A. Prokaryotes
• B. Eukaryotes
• C. Both
• D. None

Answer: (A)

Polycistronic transcripts encode multiple proteins from a single RNA molecule. In many prokaryotes, genes that work together are organized in operons and are transcribed as one mRNA that contains several open reading frames. Each coding region has its own ribosome binding site, so ribosomes can initiate translation at multiple points along the same mRNA and produce several proteins from one transcript. In contrast, eukaryotic transcripts are typically monocistronic; the mRNA is processed in the nucleus, capped, spliced, and polyadenylated, and usually carries a single coding sequence that yields one protein. Because transcription and translation are coupled, and because mRNA processing tends to separate coding regions, prokaryotes are the organisms where transcripts are commonly polycistronic.