Submitted to: Mammalian Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 12, 1995
Publication Date: N/A
Interpretive Summary: Results from previous genetic mapping experiments mapped a genetic locus responsible for multiple ovulation in sheep to chromosome 6. The purpose of the present experiment was to add markers to the map of sheep chromosome 6. The number of markers was increased from 12 to 33 and two of the markers were physically assigned by hybridizing them directly to the chromosome. Physical assignments provide orientation of the linkage map t the morphological landmarkers, centromere and telomere on the chromosome. This additional data provides a more comprehensive genetic map and provides markers closer to the gene for multiple ovulation, which will be useful in applying marker-assisted selection. Also, a comprehensive, physically anchored map is essential to efforts directed toward isolation of the gene.
The genetic linkage map of sheep Chromosome (Chr) 6 has been extended to include 35 loci with the addition of 11 RFLP and 12 microsatellite loci. The sex-averaged linkage map now spans 154 cM from phosphodiesterase cyclic GMP beta polypeptide (PDEB) to OarCP125, an anonymous sheep microsatellite. The male and female map lengths, at 180 cM and 132 cM respectively, did not tdiffer significantly. The physical assignment of PDEB to Chr 6q33-qter orientates the linkage map on sheep Chr 6 with PDEB near the telomere and OarCP125 towards the centromere. The order and genetic distances between loci are similar for the sheep Chr 6 and cattle Chr 6 maps, except for the position of the casein genes. The sheep Chr 6 linkage map is also comparable to portions of human Chr 4, mouse Chrs 5 and 3, and pig Chr 8. The synteny between sheep Chr 6 and human Chr 4 has been extended from PDEB (4p16.3) to epidermal growth factor (EGF, 4q25-q27). However, a region from platelet-derived growth factor receptor alpha polypeptide (PDGFRA) to bone morphogenetic protein 3 (BMP3), which spans 19 cM on sheep Chr 6, appears to be inverted with respect to the human and mouse loci. Other differences in the gene order between sheep, pig and mouse suggest more complex rearrangements.