Localization of CT beta and C kappa on mouse chromosome 6

In the mouse three lymphocyte gene families have been positioned on the proximal region of chromosome 6. Originally the immunoglobulin kappa light chain (Igk) and the thymocyte surface antigens Lyt-2 and Lyt-3 were assigned to chromosome 6, and recently the beta chain of the T-cell receptor for antigen was positioned proximal to Igk. Molecular clones which recognize the constant (C) region of the beta chain of the T-cell receptor for antigen (CT beta) and the constant region of the immunoglobulin kappa (C kappa) chain were used to determine recombination frequencies with respect to the morphological marker hypodactyly (Hd). SJL/JL W pi mice were mated with C.B6.C3-Hd/+ mice, and the progeny expressing the Hd phenotype were mated with SJL/JL W pi mice. Backcross progeny which expressed the Hd phenotype were nephrectomized, and kidney DNA was examined by Southern hybridization for the polymorphic restriction endonuclease fragment (REF) patterns of the parental mice. Of the 88 progeny tested in this three-point cross, 3 CT beta and 4 C kappa homozygote REF patterns were detected. These homozygotes were mutually exclusive. This implies the following gene order: centromere-CT beta-Hd-Igk and CT beta 1 would be 7.95 +/- 2.88 centimorgans from C kappa.