Probable Assignment of the Alpha Locus of Haptoglobin to Chromosome 16 in Man

Abstract

THERE has been discussion concerning the possible assignment of the human haptoglobin locus, Hp_α, to a D group chromosome^1–3. The data showed anomalies of haptoglobin inheritance in various heterozygous deletions of a D chromosome and were open to alternative interpretations such as the presence of the rare, apparently inactive, allele Hp⁰. These data have been reviewed⁴. No support for the assignment was elicited by linkage studies involving a D/D or a D/G translocation or involving a chromosomal variant of a D group chromosome. Computer analysis of sixteen such pedigrees that bear on the linkage of Hp to the D chromosomal lesion gives lod scores: which do not confirm the assignment. (Lod score at recombination fraction θ = log₁₀ (standardized likelihood of pedigree data given θ). A likelihood of 1 at θ = 0.5 (lod = 0) is taken as the base of standardization. A lod of 3, for example, corresponds to a likelihood 1,000 times greater than the likelihood at θ = 0.5.) Such apparently adverse lod scores could, however, be obtained even if the assignment were correct if Hp were remote from the site of the lesion in at least some of the pedigrees.