"A question commonly posed by clinicians, families and patients alike is, how do genes work in influencing risk for eating disorders? The lay conception of genetics tends to over-emphasize the deterministic aspect of genetic risk. Modeled after Mendelian inheritance one gene-one disorder examples (e.g. Huntington's), the misperception emerges that there is one gene for anorexia nervosa and if you have that gene you are destined to develop the condition. Clinicians are well-positioned to dispel these myths and offer more realistic albeit complicated explanations for complex inheritance patterns. By definition, eating disorders are complex traits. That means that their inheritance pattern in families does not follow traditional Mendelian patterns, and that they are influenced by multiple genetic and environmental factors of small to moderate effect. There is not one gene for anorexia nervosa or one gene for bulimia nervosa. More likely there are a number of genes that code for proteins that influence traits that index vulnerability to these disorders. Complicating the risk picture even further, these genes exist in concert with other genetic factors that may confer protection against eating disorders, along with main effects of risk and protective environments, as well as gene x environment interplay as we discuss in the following section."