The C system of cattle blood groups. 2. Partial genetic map of the system.

20 cases of irregular inheritance of phenogroups in the C system of cattle blood groups were used to deduce a partial genetic map of this system, taking into consideration the 11 internationally recognized antigenic factors and the 4 additional factors recently described by Grosclaude et al. (1980). This partial map bears resemblance to that established by Bouw et al. (1974) in Dutch cattle. The operational length of the DNA sequence coding for the C system was estimated to be 0.3 centimorgan, a value which is approximately half of that obtained for the B system by Grosclaude et al. (1979). It is concluded that the phenogroups of the C system. like those of the B system, are controlled by a cluster of loci.

The C system of cattle blood groups. 1. Additional factors in the system.

Four additional cattle blood group antigenic factors, provisionally termed F1, F6, F10 and F15, were shown to belong to the C system. Factor F1 appears to be a linear subtype of C" (initially designated F2, or P1B1). It is suggested that future international nomenclature should adopt C"1 and C"2 in place of F1 and C". No phenogroup was found to include C" together with C2 or C1, but a few phenogroups lack the three factors. Thus C1, C2 and C" do not form a closed system within the C system as concluded by Duniec et al. (1973). The effectiveness of the additional factors to uncover the genetic variability of the C system, and to translate phenotypes into genotypes is exemplified in the Charolais breed.

The genetic map of the B system of cattle blood groups as observed in French breeds.

40 cases of irregular inheritance of phenogroups in the B system of cattle blood groups, that were presumed to have arisen from single crossing-over, have been used to establish a partial genetic map of this system. In addition, the relative positions in the map of several antigenic factors were inferred from relationships observed between particular phenogroups occurring in French breeds. The tentative map thus obtained shows an overall similarity to that established by Ruiterkamp et al. (1977) in Dutch Friesian cattle. This result, in addition to other arguments, supports the hypothesis that the genetic structure of the B system of cattle blood groups is basically the same in all taurine breeds. Evidence is given, for the first time, for the occurrence in the B system of genetic events other than single crossing-over (double crossing-over or gene conversion, and possibly deletion). The rate of recombination between the genetic determinants of the terminal factors of the system, Q and I', was calculated in the progeny of some Normande bulls heterozygous for these two determinants (447 gametes); a value of 1.34 centimorgan was obtained. However complementary data indicate that 0.7 centimorgan would be a better estimate.