Extraordinary advances have been made in the field of human
molecular genetics during the past five years. The ability to amplify a
specific region ofDNA a millionfold in a few hours using the polymerase
chain reaction has led to the rapid identification of mutations in human
disease and of DNA sequence polymorphisms on every human chromosome.
DNA fragments of up to 1 megabase in length can now be resolved
by pulsed-field gel electrophoresis to create long-range physical maps of
important regions of the genome, and can be cloned in the form of yeast
artificial chromosomes. The discovery of highly variable "minisatellite"
DNA sequences has led to the development of DNA fingerprinting. The
application of these techniques to the study of the human genome has
culminated in major advances such as the cloning of the cystic fibrosis
gene, the construction of genetic linkage maps of each human chromosome,
the mapping of many genes responsible for human inherited disorders,
genetic fingerprinting of forensic specimens, and the detection
of mutations involved in the development of human tumors.