Encyclopedia of Clinical Neuropsychology

2018 Edition
| Editors: Jeffrey S. Kreutzer, John DeLuca, Bruce Caplan


  • John DeLucaEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-57111-9_1855


Allele is an alternate form of a gene, which is the basic unit of inheritance. A gene is located at a particular site on the chromosome and can have several alleles for that locus. For example, A, B, and O are different alleles for the ABO blood-type marker locus of a gene. Alleles greatly influence the expression of physical and behavioral phenotypes or traits such as eye color. For instance, the apolipoprotein E (APoE) gene is a well-known risk factor for developing Alzheimer’s disease. The APoE gene has three common alleles: epsilon 2, epsilon 3, and epsilon 4. There is some evidence that carriers of the APoE epsilon 4 allele are at a greater risk for the development of Alzheimer’s disease. In contrast, the APoE epsilon 3 allele has been suggested as a “protective” factor in the development of Alzheimer’s disease (Plomin et al. 2003).


References and Readings

  1. Plomin, R., Defries, J. C., Craig, W., & McGuffin, P. (2003). Behavioral genetics in the postgenomic era. Washington, DC: American Psychological Association.CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Research DepartmentKessler FoundationWest OrangeUSA