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We have analyzed several closely related members of the gene family encoding the variable regions of human immunoglobulin kappa light chains (V kappa genes). Two of these genes differ at a single nucleotide out of 940 bases sequenced, and are believed to be alleles of a locus called HK 101. This substitution results in an amino acid replacement in the first complementarity-determining region of the kappa chain. We also compared the structures of two nonallelic human V kappa loci (HK 101 and HK 137) and found a high degree of sequence homology over a region at least 13.5 kb long. This long block of homology indicates that these two loci arose from a recent gene duplication. The DNA sequences of these two nonallelic V kappa genes exhibit a very unusual distribution of nucleotide substitutions. Seven of the ten substitutions found among 940 bases are clustered in a 39 base stretch encoding the first complementarity-determining region and the second framework region of the protein. We suggest that this cluster of substitutions was generated by a gene conversion in which a small segment of one gene was replaced with the homologous segment from another V kappa gene.

Original publication




Journal article



Publication Date





181 - 189


Alleles, Binding Sites, Antibody, Biological Evolution, Chromosome Mapping, Cloning, Molecular, Gene Conversion, Humans, Immunoglobulin Light Chains, Immunoglobulin Variable Region, Immunoglobulin kappa-Chains, Polymorphism, Genetic, Recombination, Genetic