engleski

Comparative analyses of inbreeding on the X-chromosome in Croatian sheep breeds

Inbreeding is the mating of related individuals that share common ancestors, resulting in increased homozygosity. Inbreeding depression and increased prevalence of genetic defects are known negative consequences of inbreeding. Therefore, the estimation of inbreeding coefficients is important for the survival of genetically small populations. The main objective of this study was to estimate the extent of genomic X-chromosome inbreeding (FXsex), a rarely estimated parameter, and its relationship with autosomal inbreeding (FX) in seven Croatian sheep breeds (99 individuals) genotyped with a high-density SNP array (606, 006 SNPs). All genomic inbreeding coefficients were calculated with respect to the ROH>4 Mb. In all 99 individuals (East Adriatic metapopulation), the mean FXsex (0.054) was 2.26 times higher than FX(0.024) and a similar trend was observed in variation, as the standard deviation of FXsex (0.116) was 2.54 times higher than that of FX (0.046). The highest observed FXsex was 0.572, while 10% of animals had an FXsex>0.250. In contrast, the highest observed FX was 0.301, with only one individual having an FX>0.2500. The highest mean X-chromosome and autosomal inbreeding coefficient (FXsex=0.079 and FX=0.042) was observed in Rab Island Sheep, while the smallest inbreeding coefficients were found in Pag Island Sheep (FXsex=0.024 and FX=0.012). Our results are preliminary because both the number of breeds (7) and the number of individuals representing each breed (13 to 20) were small. Nevertheless, the higher inbreeding estimates observed for the X-chromosome in sheep demonstrate the importance of analysing possible negative inbreeding effects of the X-chromosome.

Inbreeding ; X-chromosome ; Croatian sheep breeds ; high-density SNP array

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