ABSTRACT
Essential to performing genetic linkage and association studies is the ability to relate phenotype to genotype. A list of the common phenotypes for respiratory genetics and how they are assessed is presented in Table 2.1. In this chapter, each of these phenotypes will be discussed in turn, detailing how they can be utilized by the respiratory geneticist, in either a family-based, case-control, or population-based
cohort study design. It is important to recognize that the choice of a particular phenotype and its assessment in a respiratory genetics study is dependent on many factors. Participant burden (how much the subjects can actually tolerate), scientific research question, cost, and the specific hypothesis of interest are all important factors that influence phenotypic choice and assessment. An important area not covered in this chapter is the role of environmental exposures. Ultimately, phenotype is determined by genes interacting with other genes and environmental factors in a developmental context. As important as measuring phenotypes, respiratory geneticists must be willing to consider and assess environmental exposures such as cigarette smoking, allergen levels, diet, and infections (viral, bacterial, and parasitic) as well as clinical phenotypes and DNA markers in their genetic studies. Consideration of all of the relevant environmental exposures is beyond the scope of this chapter; however, it is very clear that any respiratory genetics study that does not assess environmental tobacco smoke exposure and/or active cigarette smoking for virtually any respiratory disease outcome is missing an important opportunity for studying a potentially highly relevant environmental exposure at relatively low cost.
