The molecular organization of the H-2K region of two t-haplotypes: implications for the evolution of genetic diversity.

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Abstract
The genetic diversity between the t12 and tw5 haplotype chromosomes was studied by analyzing the molecular organization of the H‐2K region. Twenty‐one cosmid clones spanning over 150 kb of the H‐2K region of both t‐haplotypes were defined, and high resolution restriction maps were determined. Detailed comparison of the t12 and tw5 restriction maps revealed the following. (i) The H‐2K regions of both t‐haplotypes retain a very similar molecular organization to that reported for B10, BALB/c and AKR. The nucleotide sequence diversity estimated from restriction site polymorphism is 0.68% between the t12 and tw5 haplotypes; these two t‐haplotypes are no more similar to one another than BALB/c is to AKR. (ii) Genetic recombination is strongly implicated in generating H‐2 polymorphism. (iii) Genetic polymorphisms, defined as small restriction fragment size differences, are observed at multiple sites along the H‐2K region. An Alu‐like B2 sequence and BAM5‐R homologous sequence were identified as the inserted/deleted DNA segments of two of these sites, suggesting that insertion/deletion of mobile elements is a general mechanism for generating genetic diversity.