RECOMBINATION FRACTIONS IN THE HLA SYSTEM BASED ON THE DATA SET PROVINCES FRANCAISES - INDICATIONS OF HAPLOTYPE-SPECIFIC RECOMBINATION RATES

In the large genetic survey 'Provinces Francaises' the recombination f ractions in the HLA system have been estimated by a family analysis pr ogramme (FAP). A total of 1332 families were analysed and in general t he findings were in agreement with recombination fractions reported pr eviously. The maternal recombination rates were on average 1.8 times h igher than the corresponding ones for males. The comparison of the rec ombination fractions with the corresponding physical distances suggest s the existence of hot spots of recombination. The analysis did not sh ow deviations from expected values for HLA-A and B alleles on HLA-A/B recombinant haplotypes. However, analysis of HLA-B/DR recombinant hapl otypes showed a skewed distribution of B and DR alleles. The significa nce of the findings is difficult to evaluate as all results are estima ted numbers and frequencies but a manual analysis of the recombinant f amilies confirmed the observations. HLA-B/DR recombinant haplotypes ca rried often HLA-DR3 and DR11 whereas DR2 and DR7 were more rarely pres ent on recombinant haplotypes. DR4 had an increased incidence on BF/DR recombinant haplotypes but not on A/B or B/BF recombinant haplotypes. Some of the haplotypes with the strongest linkage disequilibria as A1 ,B8,DR3 and A3,B7,DR2 seem to be less frequently involved in recombina tions than other haplotypes. Variations of recombination rates dependi ng on certain alleles or haplotypes might partially explain the conser vation of some haplotypes or part of haplotypes in Caucasoids.