Mapping OneFormofAutosomal DominantPostaxial Polydactyly TypeA toChromosome7pl5-qi 1.23byLinkage Analysis

Summary Postaxial polydactyly type-A (PAP-A) inhumans isan autosomal dominant trait characterized byanextra digit intheulnar and/or fibular side oftheupper and/or lower extremities. Theextra digit iswellformed and articulates withthefifth, orextra, metacarpal/metatarsal, andthus itisusually functional. Inorder tomapthe gene responsible forPAP-A, westudied afive-generation Indian family of37individuals (15ofwhomwereaffected). A genomewide search withhighly informative polymorphic markers onpartofthepedigree showed linkage between thePAP-Aphenotype andmarkers on chromosome 7p15-qll.23 (nocrossovers werefound withD7S526, D7S795, D7S528, D7S521, D7S691, D7S667,D7S478,D7S1830, D7S803, D7S801,or ELN). Thehighest LODscore wasobtained with marker D7S801(Zmax = 4.21; 9= 0).Haplotype analysis enabled themapping ofthePAP-Aphenotype inthis family between markers D7S2848andD7S669. Analysis of additional families withPAP-Awill narrow downthe critical genomic region, facilitate positional cloning of thePAP-Agene, and/or uncover potential genetic het