Reverse Genetic approach

reverse genetics," is an approach that searches for linkage of a trait to markers in the DNA, and which requires no knowledge of what causes the illness. In this approach (described in detail by Burmeister in this issue), it is asked whether a trait (whether eye color or manic depressive illness) segregates across generations with a marked chromosomal region. This approach uses sets of polymorphic DNA markers. As described, these are genetic loci, which are readily identifiable by molecular techniques, and which show substantial sequence variation among people. The greater the variation at a locus, the more useful to mark the chromosomal regions on which they are found. If a particular chromosomal region is statistically linked to those with the trait (e.g., affected by illness), that region is then explored to find the actual genes that might be contributing vulnerability. The term "positional cloning" is truly appropriate since the information used to identify the chromosomal region of interest is based only on the positional information contributed by the DNA markers.

출처 : http://www.nimh.nih.gov/about/complexgenetics.cfm