GENETIC HAPLOTYPING OF ATAXIA-TELANGIECTASIA FAMILIES LOCALIZES THE MAJOR GENE TO AN SIMILAR-TO-850 KB REGION ON CHROMOSOME 11Q23.1

The genotyping data given localize the major A-T gene to an similar to 850 kb region. They also localize the group A A-T gene (ATA) to a region that contains the similar to 850 kb region. They are compatible with linking A-T-Fresno to 11q22-23. NBS-V2 does not link to this region. Four non-linking families contain only single affecteds, suggesting that these may be spontaneous mutations rather than evidence for an A-T gene outside the 11q22-23 region. Finally, two other non-linking families contain recombinant haplotypes that are compatible with a second A-T gene at 11q22-23, slightly distal to the similar to 850 kb region. However, convincing evidence for a second gene is still lacking.