Marker-to-marker linkage disequilibrium on chromosomes 5q, 6p, and 8p in Irish high-density schizophrenia pedigrees

Linkage disequilibrium (LD) is a potentially powerful tool for the localiza tion of disease genes for complex disorders. Most prior studies of the rela tionship between genetic distance and LD have examined only very short dist ances, focusing on the role of LD in fine-mapping and positional cloning. W e examine here the relationship between marker-to-marker (M-M) LD and somew hat greater genetic distances. We analyzed 622 RI-M pairings on chromosomes 6p, 8p, and 5q in 265 native Irish pedigrees ascertained for a high densit y of schizophrenia, LD, significant at the 5% level, was found for 96% of a ll M-M pairings within 0.5 cM, for 67% within 0.5-1 cM, for 35% within 1-2 cM, for 15% within 2-4 cM, for 8% within 5-10 cM, and for 7% above 10 cM, T hus, in Irish families selected for a high density of schizophrenia, M-M LD may be very common within 0.5 cM and frequent up to distances of 2 cM. Am J. Med. Genet. (Neuropsychiatr. Genet.) 88:29-33, 1999. (C) 1999 Wiley-Liss , Inc.