Expressed gene. Expressed gene gene Expression. (Science: molecular biology) The full use of the information in a gene via transcription and translation leading to production of a protein and hence the appearance of the phenotype determined by that gene.xpressed gene. Expressed gene gene Expression. (Science: molecular biology) The full use of the information in a gene via transcription and translation leading to production of a protein and hence the appearance of the phenotype determined by that gene.