LINKAGE MAP OF 7 POLYMORPHIC MARKERS ON RAT CHROMOSOME-18

A genetic linkage map of seven polymorphic markers was created with F2 intercross progeny of F344/N and LEW/N rats and assigned to rat Chrom osome (Chr) 18. Five of the markers described were defined by simple s equence length polymorphisms (SSLPs) associated with five genes: trans thyretin (TTR), trypsin inhibitor-like protein (TILP), beta2 adrenergi c receptor (ADRB2), olfactory neuron-specific G protein (OLF), and gap junction protein (GJA1). One marker was defined by a restriction frag ment length polymorphism (RFLP) detected with a probe for the human co lony stimulating factor 1 receptor (CSF1R) gene. The D18N1R locus was defined by an anonymous DNA fragment amplified by the randomly amplifi ed polymorphic DNA (RAPD) technique with a single short primer. These seven DNA loci formed a single genetic linkage group 30.4 cM in length with the following order: TTR-6.8 cM-D18N1R-9.1 cM-TILP-4.3 cM-CSF1R- 0 cM-ADRB2-10.2 cM-OLF-0 cM-GJA1. The five SSLP markers were highly po lymorphic. In a total of 13 inbred rat strains analyzed (F344/N, LEW/N , LOU/MN, WBB1/N, WBB2/N, MR/N, MNR/N, ACI/N, SHR/N, WKY/N, BN/SsN, BU F/N, and LER/N), three to six alleles were detected for each marker. R emarkable linkage conservation was detected between the region of rat Chr 18 mapped and a region of mouse Chr 18. However, genes associated with these markers have been mapped to three different human chromosom es (Chrs 5, 6, and 18). The markers described here should be useful fo r genetic mapping studies and genetic monitoring of inbred rat strains .