M.Sc. / The amount of allozyme variation within, and the extent of genetic differentiation between, 19 sheep breeds from southern Africa were determined by six enzyme coding loci. Another eight enzyme coding loci were analyzed for five breeds. Between 55 and 66.67% of the protein coding loci were polymorphic (95% criterion) in all the breeds, except for the Namaqua sheep that were less polymorphic (33.33%). Values of 1.67 to 2.5 were obtained for the mean number of alleles per locus and average heterozygosities per locus was between 16.6 to 35.9%. The allelic constitution particularly at the transferrin (TF) locus varied appreciably for the different breeds. For example, the TF*H allele was exclusively noted in the Dormer sheep and the TF*G allele was found in the Afiino, Van Rooy, Border Leicester, Blackhead Persian and Skilder-Persian breeds. The only polymorphic breeds at the albumin locus were the South African Mutton Merino and Van Rooy breeds. The allelic constitution at the other polymorphic loci was similar for the breeds, but the allele frequencies of the South African Merino differs from Merino breeds in other countries at the TF locus. Unbiased genetic distance values were the smallest between the Dorper and Dormer breeds and the largest between the Romenof and Blackhead Persian breeds, and the mean genetic distance between the 19 breeds was 0.067. The mean amount of differentiation among the breeds relative to ' the limiting amount under complete fixation (F st) was calculated at 0.123, which is an indication of small genetic differentiation between the breeds studied. However, this , statistic is not reflected by the allele distribution that was not identical for 25 breed pairs (15%) of the total (171) at all the genetic blood systems studied. None of the breed pairs showed identical allele distributions at all the loci studied for at least one locus differed at each breed pair compared. Random amplified polimorphic DNA's gave no consistent or repeatable results. The results of the allozyme study presents the first study of the current genetic characterization of the different southern African sheep breeds.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:3250 |
| Date | 27 August 2012 |
| Creators | Sargent, Janice |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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