DNA HAPLOTYPES OF THE COMPLEMENT C6 AND C7 GENES ASSOCIATED WITH DEFICIENCIES OF THE 7TH COMPONENT - AND A NEW DNA POLYMORPHISM IN C7 EXON-13

Eight common DNA polymorphisms have been described for the linked C6 a nd C7 genes. We now describe a ninth polymorphism in C7 exon 13 which is located in a tight cluster with two previously reported markers. We have used all these markers to investigate the heterogeneity of C7 de ficiency. Five of the nine C7 deficient probands (resident in Ireland, South Africa, Russia and Israel) are heterozygous for C6/C7 haplotype s. Seven different C7 deficient haplotypes were found for C7 markers a lone, but all the four Israelis share one and three out of four Irish haplotypes share another. The markers appear to be a good guide to the heterogeneity of C7 deficiency and have been useful in choosing homoz ygous subjects for the investigation of molecular defects.