APA Dictionary of Psychology

one or more genetic variants that increase the probability that an individual will develop a particular disease or trait, but do not by themselves cause the condition or trait. A susceptibility gene confers risk rather than certainty, typically requires interaction with other genes and/or environmental factors, and is commonly identified through association studies (e.g., genome-wide association study). An example is the ApoE4 allele, which is a susceptibility gene for Alzheimer's disease that raises the risk for but does not guarantee disease occurrence, and Alzheimer's disease can occur without it. Compare genetic predisposition.