Sixteen polymorphic microsatellites for breeding of Chinese soft-shelled turtles (Pelodiscus sinensis)

Results and discussion: Analysis of the g.+6723G>A mutation in East Friesian revealed 29 homozygotes for the mutant allele (A/A), 41 heterozygotes (A/G) and 9 animals homozygous for the wild-type allele (G/G). The genotypic frequencies are in agreement with Hardy-Weinberg equilibrium (v = 0.94; d.f. = 1). Detection of g.+6723A within the East Friesian, grouped it with the Texel, White Faced Suffolk, Lincoln and Charollais as a breed known to segregate this Myostatin mutation. The estimated frequency of g.+6723A within the East Friesian was 0.63, which is lower than for Texel, where it is near fixation. This may reflect the emphasis put on milk production by East Friesian breeders, but it also suggests that selection could quickly produce highly muscled animals. Association analysis to determine the effect of the mutation was not performed because of the absence of phenotypic records; however, breeders report the presence of lines within the East Friesian that display enhanced muscularity. Previous work reported that g.+6723A was found on a single haplotype defined by alleles at two flanking microsatellites (BM81124 allele 218 and BULGE20 allele 141). To determine if g.+6723A in East Friesian is accompanied by the same haplotype, the two microsatellites were genotyped in ten homozygous (A/A) sheep. The results revealed that seven of the animals (70%) were homozygous for the same combination of microsatellite alleles observed in the Texel. This strongly suggests a common origin for the mutation, because the alternative scenario that the mutation has arisen independently within each breed would predict that the allele would be accompanied by different haplotypes. The close geographical proximity of the breeds and anecdotal information suggest a shared origin, which explains why the allele appears to be identical by descent in both East Friesian and Texel sheep.