The term phenotype refers to an organism’s outward appearance and characteristics. This contrasts with the individual’s genotype, the set of alleles that an offspring inherits from both parents. In the behavioral sciences, including Behavioral Medicine, the fundamental issue of heredity is the extent to which differences in genotype account for differences in phenotype, i.e., observed differences among individuals (Plomin, DeFries, McClearn, & Rutter, 1997).
In contrast to single-gene disorders such as Huntington’s disease and phenylketonuria (PKU), complex dimensions, disorders, and conditions of clinical concern in Behavioral Medicine are influenced by heredity, but not by one gene alone. Multiple genes are typically involved, and so too are multiple environmental influences, and phenotypes are often the result of the combined effects of both genotype and environmental factors.
References and Readings
- Plomin, R., DeFries, J. C., McClearn, G. E., & Rutter, M. (1997). Behavioral genetics (3rd ed.). New York: W.H. Freeman and Company.Google Scholar