Gene and genome scanning by two‐dimensional DNA typing

A major effort in the analysis of DNA currently focuses on identifying genes and their pathological variants underlying disease. Once such disease genes have been isolated a major task of molecular medicine is to identify the spectrum of DNA sequence variations responsible for the aberrant function of such genes. These efforts, however, are hindered by the vast amount of genetic information to scan for variations and the limited capacity of analytical techniques in terms of accuracy and speed. Recently, a number of techniques were developed, so‐called “genome scanning” techniques, which allow complete genomes to be analyzed for sequence variation in parallel, i.e. , at multiple sites or loci simultaneously rather than serially at predefined loci. Here we present the background and applications of a particular electrophoretic parallel processing approach, generically termed two‐dimensional DNA typing. The approach is based on separating DNA fragments by two‐dimensional electrophoresis [1], including denaturing gradient gel electrophoresis, thus allowing hundreds of fragments to be simultaneously assessed by comparative analysis for variations in size and sequence. The method is suitable for hybridization analysis with locus‐specific and multilocus probes of genomic DNA restriction fragments derived from human and other DNA, and for analysis of polymerase chain reaction (PCR) fragments derived from large genes. Two‐dimensional DNA typing has been applied, e.g. , in linkage analysis of pedigrees, analysis of tumor genomes for rearrangements, and to scan the cystic fibrosis transmembrane regulator gene for sequence variations such as point mutations.