LIMITED POLYMORPHISM AT MAJOR HISTOCOMPATIBILITY COMPLEX (MHC) LOCI IN THE SWEDISH MOOSE A-ALCES

The Swedish moose was analysed for genetic variability at major histoc ompatibility complex (MHC) class I and class II DQA, DQB and DRB loci using restriction fragment length polymorphism (RFLP) and single stran d conformation polymorphism (SSCP) techniques. Both methods revealed l imited amounts of polymorphism. Since the SSCP analysis concerned an e xpressed DRB gene it can be concluded that the level of functional MHC class II polymorphism at least at the DRB locus, is low in Swedish mo ose. DNA fingerprinting was used to determine if the unusual pattern o f low MHC variability could be explained by a low degree of genome-wid e genetic diversity. Hybridizations with two minisatellite probes gave similarity indices somewhat higher than the average for other natural population, but the data suggest that the low MHC variability cannot be explained by a recent population bottleneck. However, since minisat ellite sequences evolve more rapidly than MHC sequences, the low level s of MHC diversity may be attributed to a bottleneck of more ancient o rigin. The selection pressure for MHC variability in moose may also be reduced and we discuss the possibility that its solitary life style m ay reduce lateral transmission of pathogens in the population.