DNA fingerprinting analysis of Booroola pedigrees: a search for linkage to the Booroola gene

Seven minisatellite probes from a variety of sources were used to analyse 11 paternal half-sib families in which the Booroola gene was segregating. A total of 402 bands that showed segregation in the pedigrees were examined for linkage to the Booroola gene. None of the bands showed segregation with the Booroola gene. The most likely evidence for a linked band was produced by the HaRas HVR probe in Family 902 (=0.0; LOD 2.3). The conclusion, however, is that the minisatellite probes used in this study could not be used as markers for the Booroola gene. The study highlighted problems associated with the use of minisatellite probes in linkage studies in half-sib families. The complex banding patterns found on fingerprinting gels was a major source of scoring error. In a few cases both of the sire's alleles could be identified at a particular locus, but in most cases only one of the alleles could be identified. For the most part, the bands had to be treated as dominant alleles. The contribution of dam alleles to the banding pattern could only be estimated. There was an indication that minisatellite loci in sheep are clustered in particular regions of the sheep genome as the rate at which bands segregated with each other was higher than one would expect from loci randomly distributed throughout the genome.     

Genetic analysis of fingerprints in Mérinos d''Arles X Booroola Merino crossbred sheep

The M13.13 minisatellite probe, consisting of a polymer of the M13 VNTR consensus sequence, cross-hybridized to ovine DNA and allowed detection of several polymorphic loci. Individual specific patterns were obtained in sheep using this probe. Pedigree analysis showed that individuals were heterozygous for most of the DNA fragments detected (88%). By studying the segregation of male's variable DNA fragments, a minimum of 10 loci were defined. The ovine DNA 'fingerprint' obtained with M13.13 is polymorphic enough to be used efficiently in animal identification, paternity testing, and possibly as a source of genetic markers for linkage analysis.     

Genetic linkage analysis between protein polymorphisms and the FecB major gene in sheep

A genetically linked marker locus is sought for the Booroola gene (FecB), a major gene which confers increased prolificacy in sheep. We examined 18 polymorphic proteins in sheep and found 10 to be informative in half-sib families where the Booroola gene was segregating. Recombination was observed between each of the protein loci and the Booroola gene. The loci and exclusion distance for each (calculated as the recombination fraction where the lod score was equal to -2.0) are as follows: NADH diaphorase, DIA1 (9.2 cM); arylesterase, EsA (11.9 cM); haemoglobin beta chain, HBB (17.5 cM); leucine amino peptidase, LAP (19.7 cM); malic enzyme, ME1 (14.8 cM); ovine plasminogen antigen, OPA (12.6 cM); alpha-1-protease inhibitor, PI2 (5.7 cM), erythrocyte 'X' protein, Prot-X (25.3 cM); post transferrin, PTF (2.2 cM); transferrin, TF (33.8 cM).     

Effect of litter size on blood haematocrit and liveweight in Booroola Merino and Merino ewes during pregnancy and the post-partum period

Blood haematocrit and liveweight were determined throughout pregnancy and the post-partum period in 217 Booroola Merino and Merino ewes in order to relate these parameters to litter size at birth. In pregnant ewes, haematocrit declined from three until five months gestation, rose immediately after parturition then declined until two months post-partum. During the third to fifth month of gestation, haematocrit decreased in proportion to litter size. Nonpregnant ewes, measured at similar intervals, did not show the same pattern. Haematocrit of nonpregnant animals was higher than that of triplet-bearing ewes at three, four and five months gestation, but was only significantly different to single- and twin-bearing ewes at five months. The liveweight of pregnant ewes increased up to parturition and then declined until two months post-partum. The liveweight of nonpregnant ewes increased over the experimental period. It was concluded that the number of foetuses a ewe carried had significant effects on the decline in haematocrit during pregnancy. Haematocrit was not a precise indicator of litter size in sheep. Haematocrit, ewe liveweight and ovulation rate together in a multiple regression only accounted for 37% of the variation in litter size.     

Absence of evidence for linkage between Booroola gene and genetic markers at 11 sheep blood polymorphic loci

Summary. Genetic linkage between the Booroola locus ( Fec ) and 11 sheep blood polymorphic loci (i.e. Tf, Hb, CA, OLA, and A, B, C, D, M, R, F41 red cell blood groups) was investigated in six large sire families (163 informative female offspring). The six sires tested were heterozygous for the Booroola allele ( Fec^B ) and for several genetic markers. No evidence in favour of linkage was found. Moreover, depending on the marker locus considered, linkage closer than or as close as the recombination frequency of 10–30% was excluded.