Polycistronic mRNA

Polycistronic mRNA is a type of mRNA that encodes multiple proteins. It is found primarily in prokaryotes, but also in some eukaryotes. The term "polycistronic" refers to the fact that multiple cistrons, or protein-coding sequences, are present within a single mRNA molecule.

Overview

Polycistronic mRNA is a key feature of the operon system of gene regulation, which is common in prokaryotes. In this system, a single promoter sequence initiates the transcription of a series of adjacent genes into a single mRNA molecule. This allows for the coordinated expression of genes that are involved in the same metabolic pathway or that serve a related function.

Structure and Function

The structure of polycistronic mRNA is distinct from that of monocistronic mRNA, which encodes a single protein. Each cistron in a polycistronic mRNA molecule is flanked by a ribosome binding site, allowing for the independent translation of each encoded protein. This is in contrast to eukaryotic mRNAs, which are typically monocistronic and are translated into a single protein.

The function of polycistronic mRNA is to allow for the coordinated expression of related genes. This is particularly important in prokaryotes, which lack the nuclear compartmentalization found in eukaryotes and therefore have a more direct link between transcription and translation.

Examples

One of the most well-known examples of a polycistronic mRNA is the lac operon in Escherichia coli. This operon contains three genes involved in lactose metabolism, which are transcribed into a single mRNA molecule when lactose is present in the environment.

See also

• Operon
• Gene expression
• Transcription (genetics)
• Translation (biology)

Polycistronic mRNA Resources
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