Possible heterogeneity in the phosphoglycolate phosphatase (PGP)-haptoglobin alpha (HPA) linkage

Previous investigators have reported loose linkage in both sexes for phosphoglycolate phosphatase (PGP) and haptoglobin alpha (HPA). We present results of linkage studies between PGP and HPA in two data sets, one from Houston and the other an update of an earlier report from Los Angeles. Using quadratic interpolation to estimate the male (θ(m)) and female (θ(f)) recombination values from bivariate lod tables, we found for the Houston data that θ(m) = 0.43 and θ(f) = 0.03 at the maximum lod score of z = 2.23. For the Los Angeles series, we found that θ(m) = 0.31, θ(f) = 0.48, and z = 0.27. We invoke heterogeneity in the recombination value in different families as an explanation of our findings. We also recommended that bivariate lod tables should always be generated, even though not reported. This is because the usual assumption of θ(m) = θ(f) (and, rarely, θ(f) = 1.80(m)) under which lod scores are computed may be invalid in many cases.