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Journal of Undergraduate Research

Keywords

individual genes, maternal gene influence, serotonin transporter gene

College

Family, Home, and Social Sciences

Department

Psychology

Abstract

The present analysis considers a mother gene-by-infant gene interaction of the serotonin transporter gene polymorphism (hereafter 5-HTTLPR). This is to our knowledge the first study to analyze this type of interaction. Two principle variants of this gene, a short allele (related to decreased 5-HTT expression), and a long allele, have been identified in both human and nonhuman primates. This provides 3 distinct genotypes: the homozygous short allele (ss), the heterozygotes (Ls), and the homozygous long allele genotype (LL); which have been shown to influence a variety of behaviors, principally those related to impulsive aggression (Higley & Barr, 2008) and anxiety regulation (Gunthert et al., 2007). The contribution of this polymorphism to anxiety has been established in numerous studies, as, for example, by high levels of anxiety in 5-HTT knockout mice (Adamec, Burton, Blundell, Murphy, & Holmes, 2006), and among humans, increased anxiety and amygdala activation in individuals with at least one copy of the s allele (Lesch, 1996)(Hariri et al., 2002). While such findings indicate genetic influences on behavior, single candidate genes typically account for only a small fraction of the overall picture (McGuffin, Riley, Plomin, 2001), and may be better understood as a contributory risk factor, or sensitivity factor, in the development of behavioral disorders. A mother provides context for the expression of infant genes. The study of mother-infant attachment in a non-human primate research model has distinct advantages over human studies as far as such studies can closely control external factors. Moreover, because of their close similarities to humans, neurobiological and genetic influences can be more accurately assessed for their effect on complex behavioral processes. The study of the genetic contribution to a mother’s maternal behavior would benefit greatly by the increased capacity to control environmental factors which contribute to the expression of these biological systems. Indeed, the inclusion of additional factors, such as select genes-of-the-mother can do much to reveal the power of an individual gene. We therefore hypothesized that the genotype of the infant would with the genotype of the mother elicit a predictable infant behavioral phenotype.

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