THE BOVINE B-BLOOD AND C-BLOOD GROUP SYSTEMS ARE NOT LIKELY TO BE THEORTHOLOGUES OF HUMAN RH - AN INTERESTING TWIST IN THE COMPARATIVE MAP

We tested the hypothesis that either the bovine B or C blood group sys tem is the orthologue of human RH. A comparative linkage mapping strat egy was applied, using blood typing and restriction fragment length po lymorphism (RFLP) analysis of four loci linked to RH on HSA1; PGD, FGR , ALPL and FUCA1. Four sires with a total of 255 half-sib offspring we re used for the linkage analysis. Strong support for linkage between A LPL, FUCA1 and FGR was obtained for all sire families (led scores >11 for all pairwise comparisons). This new linkage group was assigned to bovine synteny group U17 based on previous somatic cell mapping of the FGR locus. The most favoured order is ALPL-FUCA1-FGR (2.18:1), with A LPL and FGR 5.4 CM and 6.3 CM, respectively, from FUCA1. The B and C b lood group systems and PGD were genetically independent of each other and all other markers, indicating that neither B nor C is likely to be the bovine orthologue of human RH. However, given available comparati ve mapping data, there is some chance that the bovine orthologue of RH is on bovine synteny group U6. Although gene order appears to be cons erved with humans, the differences in recombination rates between thes e three loci in cattle, humans and mice strongly suggest that it is no t possible to use human map distances to predict map distances in catt le, making it imperative that bovine gene mappers continue to emphasiz e adding type I markers to the bovine linkage map.