Taq1A

Taq1A is a genetic polymorphism historically described as a marker near the dopamine D2 receptor gene (DRD2). It arose from a restriction fragment length polymorphism detected with the TaqI enzyme and is commonly discussed in terms of two alleles, A1 and A2. Although named for its association with DRD2, the Taq1A variant is now known to reside in the adjacent ANKK1 gene, and is used as a marker in studies of dopaminergic signaling and reward-related behavior.

The A1 allele is associated with reduced dopamine D2 receptor availability in the striatum, as measured by positron emission tomography (PET) imaging. This lower receptor density is thought to influence reward processing, impulse control, and motivational states, which has driven substantial research into its role in psychiatric and addictive phenotypes.

Population and genetics notes indicate that the Taq1A polymorphism is common across many populations, with allele frequencies varying by ethnicity. It is typically studied as part of a broader set of genetic factors that contribute to individual differences in reward pathways rather than as a single determinant of any condition.

Clinical relevance is largely as a risk marker rather than a diagnostic indicator. Associations have been reported with substance use disorders, alcoholism, obesity, and impulsivity, but findings are inconsistent and effect sizes are generally small. The interpretation of Taq1A results is complicated by linkage disequilibrium with neighboring genetic variants and by gene–environment interactions. Consequently, Taq1A is generally considered a research tool within the broader framework of polygenic risk and dopaminergic biology, not a standalone predictor of disease.