Monocistronic transcripts are characteristic of which domain?

• A. Polycistronic
• B. Bicistronic
• C. Multicistronic
• D. Monocistronic

Answer: (D)

Monocistronic transcripts encode a single protein per mRNA, which is the usual pattern in eukaryotes. In eukaryotic cells, mRNA undergoes processing—adding a 5' cap, removing introns by splicing, and adding a poly-A tail—before translation. The ribosome typically initiates at a single start codon after the cap, producing one protein per transcript. This setup supports independent regulation of each gene and matches how genes are organized in the eukaryotic genome.

In contrast, prokaryotes—especially bacteria—often have polycistronic transcripts, where one mRNA contains multiple coding sequences (operons) that are translated into several proteins. That difference in transcript architecture reflects the distinct modes of gene organization and regulation between the domains. So monocistronic transcripts are characteristic of the eukaryotic domain.