Gene expression

Definition

The multistep process by which information encoded in a gene is converted into a functional product—either a protein (via transcription and translation) or a functional RNA molecule (via transcription alone). In arthropods, differential gene expression underlies developmental transitions such as molting and metamorphosis, mediates caste determination in social insects, and drives physiological responses including diapause induction and detoxification enzyme production. Expression levels are regulated by transcription factors, epigenetic modifications, and environmental cues, allowing organisms to adjust phenotype without altering genotype.

Etymology

From Greek 'genea' (generation, descent) and Latin 'expressio' (a pressing out, representation)

Example

In honey bees (Apis mellifera), differential gene expression of the vitellogenin gene between queens and workers—driven by larval nutrition—establishes reproductive caste fate, with high expression promoting queen development and suppressed expression leading to worker morphology and behavior.

Related Terms

• Transcription
• translation
• epigenetics
• phenotypic plasticity
• Metamorphosis
• Diapause
• RNA interference
• regulatory gene
• housekeeping gene
• differential expression

Usage Notes

Distinguish 'gene expression' (the process and its outcome) from 'gene regulation' (the control mechanisms). In arthropod research, expression studies often compare transcriptomes across life stages, castes, or populations; 'upregulation' and 'downregulation' describe relative changes, not absolute presence or absence. Reporter genes (e.g., GFP) are commonly used to visualize expression patterns in vivo in Drosophila and other model insects.