Alternate alleles can generate differing observable features in the organism, known as the phenotype. For example, the gene for eye color in Drosophila melanogaster can have two alleles: one for red eyes and one for white eyes. An organism’s genotype is the pattern of alleles for a given trait carried by the organism (Klug & Cummings, 2003). In other words, an organism’s genetic material (sequences of DNA) is referred to as their genotype while their observable characteristics (eye color, height, etc.) are referred to as their phenotype. Alleles can influence expression in a dominant/recessive or an additive manner. The presence of a single dominant allele causes the expression of the phenotype while recessive alleles are required at both…show more content… An additive process refers to alleles at multiple loci that have a cumulative effect on a trait. Complex behavior is thought to be influenced by a multitude of genes, all individually contributing to behavioral variation, a concept known as polygeny. Conceptually, this means multiple genes can influence a single behavior. Pleiotropy, on the other hand, refers to the idea that one gene can have an effect on many behaviors (Plomin, 1990). Though it may seem initially that the laws of hereditary transmission cannot be applied to complex traits, if it is instead conceptualized as many small effects creating individual differences, the same laws can be applied. In terms of behavior, it is improbable that single genes cause the vast amount of individual variation observed within populations due to the complexity of behavioral traits. Rather, a polygenic perspective is required when investigating behavior (Hill, Goddard, & Visscher, 2008). Turkheimer (2000) posits that behavior emerges out of complex, nonlinear developmental processes that are hard to disentangle. Furthermore, Plomin
