Genetic variation in blood proteins within and between 19 sheep breeds from Southern Africa

Author: J. Sargent, F.H. van der Bank and A. Kotzé
Year: 1999
Issue: 3
Volume: 29
Page: 245 - 257

The amount of allozyme variation within, and the extent of genetic differentiation between, 19 sheep breeds from Southern Africa were determined by six genetic blood systems commonly used to distinguish between animal breeds. Another eight enzyme-coding loci were analysed 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 which 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 were calculated at 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 Afrino, Van Rooy, Border Leicester, Blackhead Persian and Skilder-Persian breeds. The only polymorphic breeds at the albumin locus were the South African Meat 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 differ 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 Romanof 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 (FST) was calculated at 0.123 for polymorphic loci, which is an indication of small genetic differentiation between the breeds studied. However, this statistic is not reflected by the allele distribution which 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. The results of this study can be used in breeding programs , and present the first study of the current genetic structure of the different southern African sheep breeds.

Keywords: allozyme variation, genetic distance, Polymorphism, sheep
Read article