ABSTRACT
This chapter describes some of the ways in which genetic analysis can be useful to investigation of the etiology and pathogenesis of lung disease. Genetic analysis has proven a powerful tool for exposing the etiology and sources of variation in many biologic phenomena. One example of impenetrance in an autosomal recessive is the phenotype of chronic obstructive pulmonary disease which occurs in about 80% of people who are homozygous for the alpha1-anti-trypsin PiZ. Dominant and recessive phenotypes caused by genes on the X chromosome show distinctive patterns of inheritance that are often easily recognized. Human males are described as hemizygous with respect to the loci on the X chromosome, since they have only one chromosome, and thus only one gene at each locus on the X. If the phenotype is expressed whenever the responsible gene is present, the phenotype is said to be fully penetrant.
