Microdissection of proximal mouse chromosome 6: identification of RFLPs tightly linked to the ob mutation.

In a previous report, the ob mutation was mapped to a position 5 cM distal to Met on murine Chromosome (Chr) 6 in tight linkage to Cpa. In order to identify additional RFLPs in the region of ob, we have made use of chromosome microdissection of a 6:16 Robertsonian chromosome. In total, 19 RFLPs were used to type 131 progency of a B6D2 ob/ + x B6 spretus ob/ + intercross. Fifteen of the RFLPs mapped to Chr 6, one of which, D6Rck13, was tightly linked to ob. For refinement of the genetic map around ob, 350 obese progency of a B6 Mus castaneus ob/ + intercross were characterized. DNAs from these animals were typed for microsatellite markers from Chr 6 that flank ob. Recombinants were then typed for D6Rck13. D6Rck13 was nonrecombinant among all the progency of both crosses corresponding to 831 meioses. This probe will be of use as an entry point for physical mapping of the ob mutation.