Which term describes a cluster of several genes transcribed into a single mRNA?

The term that describes a cluster of several genes transcribed into a single mRNA molecule is called an "operon." In prokaryotic cells, an operon consists of a series of genes that are under the control of a single promoter, leading to the transcribing of the genes as a single polycistronic mRNA. This arrangement enables coordinated regulation of gene expression, allowing bacteria to efficiently respond to environmental changes.

The operon structure primarily includes:

1. Structural Genes: These genes encode for proteins with related functions, often involved in a single biochemical pathway.
2. Promoter: A DNA sequence that initiates transcription of the operon.
3. Operator: A regulatory sequence that can bind repressor proteins, blocking transcription when needed.

In essence, operons are a key feature of prokaryotic gene regulation and exemplify how organisms can optimize their genetic resources for efficiency and adaptability.