Plant & Animal Genome VI Conference

W18

MYRIADS OF SEQUENCE DIFFERENCES BETWEEN Bos indicus AND Bos taurus GENOMES HOLD GREAT PROMISE FOR QTL MAPPING AND GENETIC IMPROVEMENT IN CATTLE

Department of Genetics, The Silberman Life Sciences Insitute, The Hebrew University of Jerusalem, 91904 Jerusalem, Isreal

Sequence comparison of 1500 bp of bovine growth hormone (bGH) uncovered six dispersed nucleotide differences uniquely distinguishing all indicine and taurine bGH haplotypes. When extrapolated, the observed sequence differences yield a total of 12 x 106 unique sequence differences between the two races. This is consistent with other evidence indicating a distant separation of the taurine and indicine races. The above figure also suggests a total of 16 to 160 nucleotide differences between the taurine and indicine versions of an average bovine gene (including exons, introns and upstream and downstream regulatory regions). The large number of distinguishing sequence differences implies: (i) that it will be readily possible to identify a polymorphic site which distinguishes between the indicine and taurine variants at any bovine genome sequence; and (ii) that the indicine and taurine versions of many genes will have somewhat different functional attributes. Consequently, the many existing mixed taurine-indicine populations should be excellent material for linkage mapping of quantitative trait loci (QTL) and for candidate gene identification by way of IBD (identical by descent) analysis. This will facilitate marker-assisted selection within mixed taurine x indicine populations, and introgression of alleles between taurine and indicine breeds. Thus, the distinct evolutionary history of the taurine and indicine races provides a unique opportunity for QTL mapping and candidate gene evaluation, and for the development of cattle genome combinations, particularly for tropical and subtropical regions of the world. Realization of this opportunity requires development of a specialized bovine genome map, consisting of polymorphic sites uniquely distinguishing taurine and indicine genomes, and appropriate QTL mapping studies in recent and ancient taurine x indicine synthetics.