Is the newly mapped gene a candidate for a previously-characterized mutant locus?
The main reason that many investigators will want to map a newly cloned gene is to determine whether it is equivalent to a locus that has been previously mapped but is characterized only at the level of a mutant phenotype. Cloning the genes associated with interesting phenotypes in this roundabout manner is usually a matter of luck and is referred to as the “candidate gene” approach. How does one begin to rule out or rule in possible identity to a phenotypically defined locus? Unfortunately, the mapping panel used to localize the cloned gene will usually not provide simultaneous map information for any phenotypically defined loci. Thus, one is forced to compare map positions derived from different crosses. One should begin a search for potentially equivalent mutationally defined loci by scanning database lists of all loci that are thought to lie within 10 cM of the map position obtained for the new clone. The databases to search should include the chromosome map compiled by the appropr
