FINE MAPPING OF THE CHROMOSOME-11Q22-23 REGION USING PFGE, LINKAGE AND HAPLOTYPE ANALYSIS - LOCALIZATION OF THE GENE FOR ATAXIA TELANGIECTASIA TO A 5CM REGION FLANKED BY NCAM/DRD2 AND STMY/CJ52.75, PHI-2.22

Using pulsed-field gel electrophoresis, and a range of different enzyme digests, we have established that both markers of each of the pairs CJ52.208/YNB3.12, NCAM/DRD2, and STMY/CJ52.75, on chromosome 11q22-23, show physical linkage on a single DNA fragment. We have also shown, using genetic linkage and haplotype analyses, that these markers lie within a region of approximately 18cM, which, it has been shown previously, is likely to contain the A-T gene. The relative positions of these marker loci, and the distance between them was determined in order to construct a detailed map which has allowed a more precise localization of the A-T gene. We have shown that in pairwise linkage analysis the strongest support for linkage to the A-T gene was with the STMY/CJ52.75 locus (Ž = 5.59, θ= 0.0). A three-point analysis using the results from STMY/CJ52.75 and the closely linked marker ø2.22 gave Ž=5.55,θ=0.03. Despite persisting evidence of some linkage to Thy-1 our results are consistent with the existence of a single A-T locus on chromosome 11q22-23 and our best estimate of the position of this locus places it between NCAM/DRD2 and (STMY/CJ52.75, F2.22) (Ž=6.74), a region of approximately 5cM in males. © 1990 Oxford University Press.