Introduction

The genetic paradigm is one of inheritance and variation. A critical domain of application of the genetic paradigm is the common complex diseases, including several that involve noradrenergic function. These diseases, including hypertension and psychiatric disorders such as anxiety and depression, are substantially heritable, indicating a powerful role for inherited gene variation. The genetics tools, both informational and technical, have developed very rapidly during the past two decades and have created a scientific revolution. Whole-genome sequencing projects have been completed, beginning with microbial genomes and continuing with the eukaryotic species: human, chimpanzee, mouse, rat, dog, and fruit fly. The genome sequences provide an informational resource of linear sequence and sequence variation. A series of new technologies has been created to apply the knowledge, including bioinformatics, robotics, and genotyping chemistries.

Many of the principal aspects of the genome are still poorly understood, for example, the regulation of alternative splicing, control of transcription, role of intergenic material, and function of many noncoding RNAs. Gene prediction is uncertain. Although many common disorders (e.g., cardiovascular, autoimmune, psychiatric) have genetic etiologies, their inheritance is genetically complex, such that variations in more than one gene lead to a phenotype, prominent gene x environment interactions, and gene x gene interactions may also occur.