Objectives: To characterize a disease-associated haplotype in 7 families with autosomal dominant Stargardtlike macular dystrophy and to determine whether these families share a common ancestor. Methods: Twenty-five polymorphic DNA markers spanning known dominant Stargardt-like gene loci were used to determine the haplotype associated with disease. In addition, an extensive genealogical investigation searching for a common ancestor shared by all of the 7 families was performed. Results: We

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... ally evaluated 171 patients and genotyped 145 samples. The same DNA haplotype on chromosome 6q16 was shared by all evaluated affected members within the 7 families. In addition, we were able to genealogically join all of the families into one larger family consisting of 31 branches and 2314 individuals. Twenty-seven branches have known living descen- OPHTHALMIC MOLECULAR GENETICS