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GENOMICS
The horns of a dilemma are usually on the same bull (1).
When it comes to behavior, the nature-nurture controversy has not disappeared. The public is leery of attributing behavioral influence to DNA rather than to the environment and free will; worries abound over the ethical implications of biological determinism. Many social and behavioral scientists are skeptical as well, either because the concept of "DNA as destiny" does not jibe with their understanding of the dynamic nature of behavior or because they consider human behavior to be much more complex than that of animals studied from a genetic perspective. By contrast, biologists have long accepted that genes, the environment, and interactions between them affect behavioral variation. Traditionally, behavioral variation has been partitioned using statistical analysis into genetic (G), environmental (E), and G & E components, an approach that began long before the advent of molecular biology. This retains the flavor of the nature-nurture dichotomy, which influences how research in this field is interpreted. Fortunately, we can now study genes in enough detail to move beyond the nature-nurture debate. It is now clear that DNA is both inherited and environmentally responsive.
Behavior is orchestrated by an interplay between inherited and environmental influences acting on the same substrate, the genome (see the figure). For behavior, gene expression in the brain is the initial readout of the interaction between hereditary and environmental information. Inherited influences ("nature") include variations (polymorphisms) in DNA sequence transmitted from generation to generation over an evolutionary time scale. DNA polymorphisms can affect protein activity (sometimes via posttranslational mechanisms) and gene expression in the brain: when, where, and how much of each protein is produced. The environment ("nurture") also influences gene expression in the brain during the lifetime of an individual (2, 3). Environmental effects occur over developmental and physiological time scales. Gene expression in the brain constitutes the first measurable indicator of the interaction between the genome and the environment.
Until recently, this "first phenotype" was not easy to study. However, it is now possible to investigate the relationship between gene expression and behavior in the brains of animal models, thanks to new genomic techniques that make gene expression analysis more sensitive, efficient, and comprehensive. As the following three examples illustrate, we...