Linkage of the locus for canine dewclaw to chromosome 16.

The canine species, including wolf and jackal, have four digits on the hind limb. It was thought that an extra first digit on the hind limb, named dewclaw, was a hereditary defect. For genetically related canine pedigrees with 73 members with dewclaws, we carried out a genome-wide scan for linkage with microsatellites. With an assumption of autosomal dominant mode of inheritance, significant linkages were detected for the markers on canine chromosome 16. The maximum two-point lod score of 20.76 was obtained for the REN85M08/REN85N14 markers at a recombination fraction of 0.00. For efficient analysis of linkage, a revised order of the chromosomal markers was established by assigning all the existing markers from the previous linkage and radiation hybrid maps. A chromosome-wide haplotype analysis revealed the location of the dewclaw locus within a few centimorgan intervals delimited by the UCMCF12 and CXX876 markers. Canine chromosome 16 is known to have syntenic relationships with human chromosomes 4q, 7q, and 8p.