Observed deviations from the expected Mendelian inheritance of alleles from heterozygous parents has been reported in a broad range of organisms and it is well known as transmission ratio distortion (TRD). Various biological mechanisms affecting gametes, embryos, foetuses, or even postnatal offspring can produce patterns of TRD. Bayesian models were used to evaluate TRD across the whole genome of Holstein dairy cattle by using either a SNP-by-SNP approach or haplotypes of 2 SNP sliding windows in 79,238 genotyped trios (parents-offspring). From 44,369 autosomal SNP, 942 were significantly detected with TRD that exceeded Bayes factor (BF) ≥ 10 (strong evidence) and 408 with BF ≥ 100 (decisive evidence). The number of SNP with parent-unspecific and parent-specific TRD was 270 and 672 SNP, respectively. After correction by the approximate empirical null distribution of TRD, the number of significant SNP reduced to 669, 462 and 73 with a probability of error of 1%, 0.01% and <0.001%, respectively, which mostly coincided with the genomic regions with high BF. In SNP-by-SNP analyses, the regions with moderate-to-high |TRD| (≥ 0.15) were less polymorphic, providing evidence of TRD selection and exhibiting interesting rare variants. In contrast, more polymorphic regions with moderate-to-high |TRD| were observed by the haplotype analyses. The number of regions detected by haplotype analyses after correction (at <0.001% probability of error) were 775, 348 and 562 for overall, sire- and dam-TRD, respectively. The preliminary functional analysis of detected regions with TRD identified positional genes associated with regulation of embryonic development. In conclusion, the prevalence of TRD was extended across the whole genome and a deeper study of these candidate regions and markers will be required to understand this phenomenon in cattle. Keywords: transmission ratio distortion, heterozygous parents, Bayesian analysis, haplotypes, cattle

Samir Id-Lahoucine, Joaquim Casellas, Pablo Augusto de Fonseca, Filippo Miglior, Mehdi Sargolzaei, Luiz Fernando Brito, Stephen Miller, Jacques Chesnais, Michael Lohuis, Flavio Schenkel, Juan F Medrano, Angela Canovas

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Biology - Reproduction 2, , 744, 2018
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