Genetic and structural studies on rat kappa chain allotypes.

Several features of the RI-1 system in the rat render it of special interest to the immunogeneticist. First, it remains the only kappa chain marker in a laboratory rodent. Second, the degree of structural divergence between the two known forms is unexpected for the products of allelic genes and raises interesting genetic and evolutionary questions. If they are truly allelic, what is the nature of the selective forces that have produced and maintained this polymorphism? If they are not allelic, what genetic structure and control mechanism can account for their allelic expression? The Australian Rattus group is clearly providing a valuable system for studying the nature of kappa chain diversity and evolution. In addition, the possibility of making laboratory crosses between forms that differ both phenotypically and karyologically provides the opportunity of establishing linkage relationships and chromosomal localization for RI-1 and many other biochemical loci.