APA Dictionary of Psychology

a specific gene selected for study because prior biological research suggests it may be directly or indirectly responsible for a trait, disease, or phenotype. Selection is typically based on the gene’s known or hypothesized role in relevant biological pathways; expression in affected tissues; or evidence from animal models, linkage studies, or molecular biology. In research, candidate genes are examined for variation (e.g., single-nucleotide polymorphisms, repeat expansions, mutations) to test whether these variants are associated with the outcome of interest. Candidate gene studies contrast with hypothesis-free methods such as genome-wide association studies, which scan the entire genome without preselecting genes.