Final answer:
Polycistronic mRNA is a single mRNA molecule that encodes for multiple polypeptides, common in prokaryotic transcription, not eukaryotes. It allows for simultaneous translation by polysomes for efficient protein synthesis.
Step-by-step explanation:
The correct definition of polycistronic mRNA is a single mRNA molecule that contains the transcript for multiple genes. This type of mRNA is commonly produced during prokaryotic transcription and carries information encoding multiple polypeptides. This contrasts with monocistronic mRNA, where a single mRNA molecule codes for a single polypeptide. In eukaryotes, the mRNA is typically monocistronic, while in prokaryotes such as bacteria, polycistronic mRNA allows for the coordinated expression of genes that function in the same process or pathway, often organized into operons.
Genes encoding proteins of related functions can be transcribed under the control of a single promoter, resulting in the formation of polycistronic mRNA. This efficient mechanism enables the simultaneous translation of multiple proteins by multiple ribosomes, or polysomes, which is particularly important for the rapid synthesis of proteins necessary for the bacterial cell's functions.