Linkage between the variegate porphyria (VP) and the alpha-1-antitrypsin (PI) genes on human chromosome 14

From family studies close linkage between the gene locus for variegate porphyria (VP) and the alpha-1-antitrypsin (PI) gene became evident. The maximal lod score from male meioses was 4.33 at \(\hat \theta \) =0.04 and from both sexes combined 3.56 at \(\hat \theta \) =0.12. Three pedigrees were triple informative regarding loci VP, PI, and IGHC (immunoglobulin heavy chain cluster, Gm polymorphism). In two of the respective meioses recombinations were observed, and in both cases the co-segregating VP and PI alleles were separated from the Gm haplotypes. These findings argue in favour of gene order either VP:PI:IGHC or PI:VP:IGHC.