ABSTRACT
Only a generation ago, the number of chromosomes in the human body was correctly determined to be 46. Then, in rapid succession, studies were begun to identify the genes underlying Mendelian, single-gene disorders. Initially, success was limited by the number of molecular markers that were available for analysis. However, during the past two decades, the field of gene mapping has been revolutionized by the advent of new molecular technologies that have made the rapid identification of genetic mutations possible. These developments have included the identification of thousands of molecular markers located throughout the human genome that can be easily genotyped and used to pinpoint the location of a disease gene to a small chromosomal segment. Then, through the careful examination of genes located within the narrowed critical interval, researchers have successfully identified the causative gene for nearly all of the common, Mendelian disorders such as cystic fibrosis and Duchenne muscular dystrophy.
