Identification of the locus encoding the minor H antigen recognized by J 47 using genetic linkage analysis. Two-point linkage analysis localized the coding sequence to chromosome 1q. (A) Genotypic data were extracted for chromosome one from the CEPH V9.0/V10.0 database, and a LOD table was constructed using 8 CEPH families. Markers on chromosome 1q identify a 20.4-cM region of interest with significant linkage to the locus encoding J 47. (B) According to the University of California Santa Cruz Genome Browser (http://genome.ucsc.edu/), this region corresponds to a physical map distance of 9.87 Mb. (C) Haplotype analysis identified informative recombinants in pedigrees 1332 and 1347 that implicate a 4.7-Mb region between D1S1540 and D1S517 as encoding the minor H antigen recognized by J 47. In family 1332, individual 8 who is minor H antigen⁺ shares the involved haplotype only proximal to marker D1S517 with the minor H antigen⁺ father. In family 1347, individual 10 is minor H antigen⁺ and shares the haplotype on chromosome 1q with the minor H antigen⁺ father only distal to D1S1540. Black, white, and gray circles (female) or squares (male) indicate a person who was scored as positive, negative, or indeterminate (B-LCLs not available or marginal lysis level), respectively, for the minor H antigen phenotype.