LINKAGE RELATIONSHIPS AMONG 20 GENETIC-MARKERS IN CATTLE - EVIDENCE FOR LINKAGE BETWEEN 2 PAIRS OF BLOOD-GROUP SYSTEMS - B-Z AND S-F/V RESPECTIVELY

Summary Five bovine paternal half‐sib pedigrees for a total of 527 individuals were typed for six blood group systems: A, B, F/V, L, S, Z; for nine biochemical polymorphisms: ADA, MPI, PGM‐3(slow), NP, Gc, Pi2, Tf, Ptf1 and Ptf2; and for restriction fragment length polymorphisms at five autosomal loci: Tg, GH, LDLr, BoLA‐DQ and BoLA‐DY. Two of the pedigrees were informative for segregation at the ‘muscular hypertrophy’ locus, and one was informative at the coat colour determining ‘roan’ locus. Linkage analysis was performed between all markers. Linkage was demonstrated between the S and F/V blood group systems (z = 3·11), adding one locus to the previously identified linkage group VII (LGVII) [Pi‐2 and S], the most likely order being Pi2‐S‐F/V with maximum likelihood recombination rates of 0·208 and 0·211. Also shown to be linked were the blood group systems B and Z (z = 5·7, θ= 0·245). We confirmed the observation previously made by Andersson et al. (1988) of a high recombination rate between class II genes DQ and DY, suggesting either a larger physical distance between those genes than expected from comparative data, or the presence of a ‘recombinational hotspot’ in the bovine major histocompatibility complex. No linkage was found either with the ‘muscular hypertrophy’ locus, or with the ‘roan’ locus. However, these two loci could be excluded from respectively 1·7 and 2·5 Morgans of the bovine genome. 1990 International Society for Animal Genetics