title: Rat kappa-chain J-segment genes: two recent gene duplications separate rat and mouse.
abstract: We have cloned DNA segments containing the Jk genes from LOUVAIN rat liver, and have determined their nucleotide sequence. Seven readily identifiable Jk-coding regions (six expressible) are evident in the rat, compared with five in the mouse (four expressible). The two additional J segments in the rat appear to be the result of two sequential gene duplications occurring since the divergence of rats and mice. The first involved a homologous but unequal crossing-over in a 14 bp region spanning the 3' end of the coding region of J1 and J2. The second involved a crossing-over following unequal pairing of the two newly duplicated regions. We propose that the probability of a second duplication was greatly increased following the first as a result of the increased target for unequal pairing (370 bp of good homology versus 27 bp in the original pairing). Comparisons of rat and mouse J genes show a surprisingly high degree of sequence conservation, both inside and outside the coding regions, similar to the pattern we reported previously for the kappa constant-region gene. This provides additional evidence that constraints exist on the nucleotide sequences of these genes independent of the function of the encoded proteins.
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003434:Crossing Over, Genetic; D004247:DNA; D004262:DNA Restriction Enzymes; D005796:Genes; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D051379:Mice; D051381:Rats; D013045:Species Specificity
chemical_list: D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D004247:DNA; D004262:DNA Restriction Enzymes