How many genes are transcribed as a single mRNA in the tryptophan operon?

In the tryptophan operon, a single mRNA molecule is transcribed that encodes for multiple genes involved in the biosynthesis of tryptophan. Specifically, the operon contains five structural genes, which are involved in various stages of tryptophan synthesis. When this operon is expressed, it results in a single polycistronic mRNA that includes the coding sequences for all five of these genes. This arrangement allows for coordinated regulation of the enzymes necessary for tryptophan production, enabling the cell to efficiently produce this amino acid in response to its availability.

Understanding that the operon's structure allows for the transcription of multiple genes as one continuous mRNA is crucial for grasping how bacterial gene regulation and expression work, especially in relation to operons.