The primary goal of this proposal is to maintain and extend the Jackson Laboratory DNA Panel Mapping Resource. This resource utilizes interspecific backcross DNAs from progeny of F1 hybrids between inbred Mus musculus and Mus spretus strains, backcrossed to Mus musculus (BSB Panel) or to Mus spretus (BSS Panel). The Resource supports the scientific community by providing users with the initial reagents for genetic mapping (DNAs and Southern blots). In addition, the Mapping Resource aids users with data analysis and graphical maps placing new markers relative to all others that are mapped in the two Mapping Panels. Haplotype data for locus typings in the BSB and BSS crosses are stored in the DNA Panel Mapping Resource database and are available online to the greater scientific community via the World Wide Web (WWW). The investigators propose to maintain this DNA Panel Mapping Resource, increase the genetic marker density on the maps of both the BSB and BSS DNA panels, to continue to promote the use of the Mapping Resource for genetic and physical mapping studies, and to pursue new ways to conserve the DNA Panel Resource.