Structural gene

Definition

A gene that encodes a functional RNA or protein product, as distinguished from regulatory sequences that control gene expression without themselves being transcribed into functional molecules. In arthropods, structural genes include those producing cuticular proteins, digestive enzymes, venom components, and structural subunits of respiratory pigments.

Etymology

From French 'structure' (arrangement, construction) + 'gene' (unit of heredity); coined in mid-1960s during studies of the lac operon in E. coli to distinguish protein-coding sequences from regulatory elements.

Example

In Drosophila melanogaster, the yellow gene is a structural gene encoding a protein required for melanin deposition in the cuticle; mutations in its coding sequence produce the characteristic yellow body phenotype regardless of normal regulatory inputs.

Synonyms

• protein-coding gene
• coding sequence

Related Terms

• regulatory gene
• operon
• cistron
• coding region
• exon
• promoter
• transcription factor
• Gene expression
• phenotype

Usage Notes

Contrasts with regulatory gene or cis-regulatory element, which modulate when, where, and how much product is made without encoding the product itself. The distinction is functional rather than strictly positional: a single locus may contain both structural and regulatory sequences (e.g., intronic enhancers). In modern genomics, 'coding sequence' (CDS) is often preferred for precision, though 'structural gene' persists in developmental and physiological literature.