Sheep blood polymorphism and genetic divergence between French Rambouillet and Spanish Merino: role of genetic drift

Random amplified polymorphic DNA in cattle and sheep: application for detecting genetic variation

The present study investigated the use of the random amplified polymorphic DNA (RAPD) method to detect genetic variation in cattle and sheep. The animals studied consisted of samples from five Finnish cattle breeds: native Eastern (18 animals), Northern (24), Western Finncattle (24), Finnish Ayrshire (24), and Finnish Friesian (18); as well as a white (6 animals) and a grey (9) colour type of Finnsheep. The cattle and sheep populations were analysed with 11 and 13 RAPD primers demonstrating the most repeatable amplification pattern. Two out of ten RAPD fragments tested by cross hybridization showed homology between the two species. The RAPD method did not prove efficient for finding new polymorphisms in either species, because we found only three polymorphic RAPD markers for cattle and seven markers for sheep with different allele frequencies between the breeds. Although there is a greater presence of polymorphic RAPD markers in sheep, according to the similarity indices the sheep populations showed a higher degree of homogeneity than the cattle breeds. However, the interbreed and intrabreed similarity indices for cattle did not suggest any significant differentiation of the Finnish breeds, contrary to earlier results based on blood group and protein polymorphism.

Extensive protein and microsatellite variability in an isolated, cyclic ungulate population

We investigated polymorphism at protein and microsatellite DNA loci in an isolated, unmanaged and cyclic population of Soay sheep on the island of Hirta, St. Kilda. Extensive molecular variation was revealed at both protein loci (mean heterozygosity 7.78 per cent) and microsatellite loci (mean heterozygosity 50.93 per cent). Typically, large mammals possess limited protein variation and we were surprised to observe such a level of protein heterozygosity, particularly considering the genetic history of the Hirta population. Indeed, compared to other mammals, Soay sheep lie within the top 17 per cent of the distribution of average protein heterozygosities. We discuss the level of protein heterozygosity in the context of other mammalian species, other breeds of sheep and the genetic history of Soay sheep. Possible explanations for a large average and interlocus variance in protein heterozygosity are proposed. Although little data are available from other studies to compare with microsatellite DNA variability in this population, we discuss the potential application of microsatellite markers to interpopulation and interspecific genetic studies.