Fig. 5.

Prokaryotic and eukaryotic operons. A) The prokaryotic operon model is that polycistronic mRNA is produced from a single promoter, containing several genes in the same transcript. Each protein is translated from a different location of a single mRNA. B) Eukaryotic operons also produce a single preRNA transcript with multiple genes, but are then processed to form mRNAs for each individual protein. As part of the processing each mRNA has a splice leader added to the 5’ end of the transcript. These mRNAs are then translated. Usually the first gene from the preRNA in a nematode operon transcript is spliced with the SL1 splice leader attached while all other downstream genes have the SL2 splice leader attached.