Pi-Gm linkage: evidence for linkage in males but not in females and for an effect of the S allele of the Pi system

The Gm-Pi linkage in 843 French families: effect of the alleles Pi Z and Pi S

Linkage analysis was performed between Gm and Pi in 843 French families. The overall recombination fraction is equal to 0.25 with a sex difference ratio of 1.4 (recombination fraction of 0.20 in males and 0.29 in females), confirming previous results in the literature. Our study does not confirm the existence of a heterogeneity in recombination rate of Pi S versus non-S alleles, but it confirms the previous finding that the presence of the Pi Z allele tends to decrease the recombination rate between the two loci. This decrease appears to be similar in both sexes, and not uniquely in males as previously noted. This result suggests a possible linkage disequilibrium between the Pi Z allele and a presumably large inversion between the two loci Gm and Pi.