The arrangement of H-2 class I genes in mouse t haplotypes

Molecular organization of the D-Qa region of t-haplotypes suggests that recombination is an important mechanism for generating genetic diversity of the major histocompatibility complex

We have determined the molecular maps of the H-2D and Qa regions of the t-complex haplotypes t12 and tw5 by chromosomal walking. Analysis with class I probes and other probes unique to the H-2D:Qa subregion indicates that the class I gene organization of t12 is: D1-D2-Q1-Q2-Q3-Qx-Q4-Q5-Q10, while that of tw5 is: D1-D2-Q1-Q2-Q4-Q5-Q10. Thus, the absence of the Q6-Q9 genes suggested previously in t-haplotypes was confirmed. A comparison of the molecular maps of the t12 and tw5 chromosomes revealed an extremely mosaic pattern of diversity: The regions between D1 and D2, and between Q4 and Q10, are very similar in both chromosomes. However, their Q1 to Q3 regions are strikingly different. Further comparisons of wild-type chromosomes and additional t-haplotypes by molecular mapping and genomic Southern blot hybridization with probes to the Q1-Q3 region showed a high level of polymorphism among both wild-type chromosomes and among t-haplotypes. The characteristics of the polymorphisms suggest that recombination may play an important role in generating this genetic diversity. Furthermore, recombination between wild-type and t-haplotype chromosomes may be involved.

Three new t-haplotypes of Mus musculus reveal structural similarities to t-haplotypes of Mus domesticus

Three newt-haplotypes,tp 4,tp 12andtp 14, were isolated fromM. musculusmale mice captured in Central and East Bohemia, Czechoslovakia, about 400 km from the zone of hybridization betweenM. musculusandM. domesticusspecies. Complementation tests have shown that all three newt-haplotypes belong totw 73group. When compared with 5t-haplotypes fromM. domesticusthey displayed the same pattern ofBamHI restriction fragments withH-2class I genes, and they also shared thet-specific 5·2 kbTaqI fragment of the alpha globin pseudogene. However, they differed fromM. domesticus t-haplotypes at the D17Leh443 locus since they all displayed a 10·5 kbMspI fragment, labelled by the Tu443 probe, not found in wild type-chromosomes or inM. domesticus t-haplotypes. A hypothesis is proposed thatt-haplotypes inM. domesticusoriginated by a single successful introgression from a parental species during speciation.