Associations between serum transferrin polymorphism and disturbed segregation ratios in Welsh Mountain sheep

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Abstract
Six serum transferrins have been found amongst 1,030 sheep in a Welsh Mountain sheep flock, apparently produced by six genes segregating as alleles at a single locus. All 21 possible phenotypes have been found.The genes are designated TfA, TfB, Tfc, TfD, TfE and Tfp, TfA producing the fastest, and Tfp, the slowest migrating component. TfE and Tfp are at a much lower frequency (0·01 to 0·06) than the remaining genes (0·2 to 0·3) and Tfp may represent a fifteenth allele at this locus.A comparison of observed phenotype frequencies with those expected under random mating, showed that a marked disturbance in segregation existed, with homozygous TfCC animals in consistent excess and a marked shortage of heterozygous TfBC and TfCD animals. Variation amongst remaining phenotypes appeared to be at random. However, incompatibility with the Tfc gene also extended to matings including Tfp. Examination of 282 matings confirmed that the effect of the Tfc gene favours maternal-foetal incompatibility as a cause of disturbed segregation, rather than selective fertilisation. However, reciprocal mating data were not available.