Departament de Ciència Animal i dels Aliments, Universitat Autònoma de Barcelona, Bellaterra, 08193, Spain.
Department of Animal Biosciences, Centre for Genetic Improvement of Livestock, University of Guelph, Guelph, ON, N1G 2W1, Canada.
Anim Genet. 2020 Dec;51(6):847-854. doi: 10.1111/age.13007. Epub 2020 Sep 30.
Transmission ratio distortion (TRD) is defined as the observed deviation from the expected Mendelian inheritance of alleles from heterozygous parents. This phenomenon is attributed to various biological mechanisms acting on germ cells, embryos or fetuses, or even in early postnatal life. Current statistical approaches typically use two independent parametrizations assuming that TRD relies on allele- or genotype-related mechanisms, although they have never been tested and compared. This study compared allele- and genotype-related TRD models on simulated datasets with 1000 genotyped offspring and real data from 168 sire-dam-offspring beef cattle trios. The analysis of simulated datasets favored the true model of analysis in most cases (>93%), and a low percentage of missidentification occurred under (almost) null dominance (genotype-related model) or similar and moderate-to-low sire- and dam-specific TRD parameters (allele-related model). Moreover, the correlation between simulated and predicted distortion parameters was high (>0.97) under the true model. The comparison of allele- and genotype-related TRD models is an appealing tool to infer the biological source of TRD (i.e. haploid vs. diploid cells) when screening the whole genome. The analysis of beef cattle data corroborated a TRD region previously reported in chromosome 4, although discarding allele-related mechanisms and favoring the genotype-related model as the more reliable one. The results of this study highlight the relevance of implementing and comparing different parametrizations to capture all kinds of TRD, and to compare them using appropriate statistical methods.
传递率失真（TRD）定义为从杂合父母的等位基因观察到的与预期孟德尔遗传的偏差。这种现象归因于作用于生殖细胞、胚胎或胎儿的各种生物学机制，甚至在出生后早期的生活中也是如此。目前的统计方法通常使用两种独立的参数化方法，假设 TRD 依赖于与等位基因或基因型相关的机制，尽管它们从未经过测试和比较。本研究比较了模拟数据集上与 1000 个已分型后代和 168 个公牛-母本-后代肉牛三亲系的真实数据相关的等位基因和基因型 TRD 模型。在大多数情况下（>93%），模拟数据集的分析有利于真实模型，并且在（几乎）零显性（基因型相关模型）或相似且中等至低的公牛和母本特异性 TRD 参数（等位基因相关模型）下，误识别的百分比很低。此外，在真实模型下，模拟和预测失真参数之间的相关性很高（>0.97）。当筛选整个基因组时，比较等位基因和基因型相关的 TRD 模型是推断 TRD 生物学来源（即单倍体与二倍体细胞）的一种有吸引力的工具。对肉牛数据的分析证实了先前在第 4 号染色体上报告的 TRD 区域，尽管排除了与等位基因相关的机制，并倾向于将与基因型相关的模型作为更可靠的模型。本研究的结果强调了实施和比较不同参数化方法以捕获所有类型的 TRD 的相关性，以及使用适当的统计方法对其进行比较的重要性。
