An H-2K gene of the t w32mutant at the T/t complex is a close parent of an H-2K qgene

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Abstract
Two recombinant mice have been recovered from the progeny of Ttf/t w32+ animals. They have lost the tw32 lethality factor(s) and gained tufted, presumably from the T chromosome. Southern blot analysis of class I genes of these two new partial t PA027 and t PA286 haplotypes indicates that they have retained at least part of the major histocompatibility complex of the t w32 chromosome (H-2 haplotype H-2 w28). We have prepared a phage library of Eco RI-digested DNA from homozygous t PA027 animals. Upon screening the library with a cDNA probe specific for H-2K genes, we isolated a class I gene displaying all of the distinctive features of a genuine H-2K gene, and which could thus be defined as an H-2K w28 gene. The H-2K w28 gene is 92–95% homologous to H-2K band H-2K dgenes and differs significantly from the other class I genes sequenced so far. Homology with the H-2K bsequence reaches nearly 100% in the 3′ part of the H-2K w28 gene. Moreover, the homology with an H-2K qcDNA sequence reaches 99.8%. Several hypotheses can account for the near identity of H-2K b, H-2K q,and H-2K w28 gene sequences: either recombination between H-2 w28 and H-2 band H-2 qsequences occurred before or at the.time the strain was established, or the class I genes of the t w32 chromosome and the H-2 band H-2 qgenes found in inbred strains of mice have separated from each other rather recently.