Physical and genetic map of the Wld region. Wld maps between Nppa and D4Mit127 in distal mouse chromosome 4. Five recombinations lying within the span of a single P1 (236-D23) define the proximal end of the Wld region, whereas a single recombination defines the distal end. A BAC and P1 contig estimated at 1.4 Mb was generated by using as a starting point three nonrecombinant markers, D4Mit49, D4Mit225, and D4Mit310. BACs (Research Genetics) are labeled “B” on their left side on this diagram and the other clones are P1s (Resource Centre Primary Database, RZPD). The coordinates of each clone from the respective libraries are shown. Five P1 and BAC end clones are shown to lie within the repeated region. L23/R and 75/R are the closest flanking end clones that are not repeated, and the location of 5P1 (used in Fig. 2a) is also shown.