Allelic Expression

Allelic expression refers to the differential activation or silencing of alleles—variant forms of genes—that control aroma and flavor production in cannabis. In diploid plants like cannabis, each individual carries two copies of genes responsible for terpene synthesis and volatile compound production; allelic expression determines which variants are active and to what degree. This phenomenon can result in phenotypic variation in aroma profiles even among genetically related plants, as epigenetic factors and environmental conditions influence which alleles are expressed. Breeders tracking allelic expression patterns help predict and stabilize aroma consistency across seed lines, particularly when working with heterozygous breeding stock or attempting to preserve rare volatile profiles.

Understanding allelic expression allows breeders to identify which genetic copies drive dominant aroma traits and to select parents more reliably for stable, repeatable terpene profiles across generations. This knowledge supports predictive breeding for complex aroma phenotypes that depend on multiple terpene-synthesis genes.