Integration, redundancy of function are hallmarks of important biological processes. Individual gene defects may overcome and override normal homeostatic systems and lead to dramatic, recognizable phenotypes by profoundly altering 1 or more physiological systems. Classical human geneticists interested in a monogenetic disease began at the level of altered function and struggled to determine the genomic defect of that disease. In the past 1½ decades, many monogenetic defects have been identified by positional cloning, and the abnormal gene has been characterized. A challenge for current investigators is to understand how a genetic defect, identified by a DNA mutation, leads to the altered phenotype. This effort is not trivial, since there are multiple metabolic and structural consequences of a single altered gene. Further complexity results from individual genetic changes being modified by the genetic diversity of the human host. Pleiotropy refers to the phenomenon of multiple phenotypic effects of a single gene.
Arch Dermatol. 1997;133:1293-1295
Goldsmith LA. Genetic Skin Diseases With Altered Aging. Arch Dermatol. 1997;133(10):1293-1295. doi:10.1001/archderm.1997.03890460117014