Some livestock breeds face the challenge of reduced genetic variation, increased inbreeding depression owing to genetic drift and selection. Hybridization can reverse these processes and increase levels of productivity and adaptation to various environmental stressors. Samples from American Brangus were used to evaluate the indicine/taurine composition through nine generations (~45 years) after the hybridization process was completed. The purpose was to determine how hybridization alters allelic combinations of a breed over time when genetic factors such as selection and drift are operating. Furthermore, we explored genomic regions with deviations from the expected composition from the progenitor breeds and related these regions to traits under selection. The Brangus composition deviated from the theoretical expectation, defined by the breed association, of 62.5% taurine, showing taurine composition to be 70.4 ± 0.6%. Taurine and indicine proportion were not consistent across chromosomes. Furthermore, these non-uniform areas were found to be associated with traits that were probably under selection such as intermuscular fat and average daily gain. Interestingly, the sex chromosomes were predominantly taurine, which could be due to the composite being formed particularly in the final cross that resulted in progeny designated as purebred Brangus. This work demonstrated the process of new breed formation on a genomic level. It suggests that factors like genetic drift, selection and complementarity shift the genetic architecture into a uniquely different population. These findings are important to better understand how hybridization and crossbreeding systems shape the genetic architecture of composite populations.

中文翻译：

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牛复合品种开发过程中的基因组结构动力学。

由于遗传漂移和选择，一些牲畜品种面临着减少遗传变异，增加近交衰退的挑战。杂交可以逆转这些过程，提高生产力，并适应各种环境压力。在杂交过程完成后的9代（约45年）内，使用American Brangus的样品评估了标记/牛磺酸的组成。目的是确定当遗传因素（例如选择和漂移）起作用时，杂交如何随时间改变一个品种的等位基因组合。此外，我们探索了与祖先品种的预期组成有偏差的基因组区域，并将这些区域与选择的性状相关。布兰格斯的构成偏离了理论预期，根据品种协会的定义，牛磺酸为62.5％，表明牛磺酸成分为70.4±0.6％。牛磺酸和标记的比例在染色体之间不一致。此外，发现这些不均匀区域与可能正在选择的特征有关，例如肌间脂肪和平均日增重。有趣的是，性染色体主要是牛磺酸，这可能是由于复合物的形成，特别是在最终杂交中形成的复合物，导致后代被指定为纯种的Brangus。这项工作在基因组水平上证明了新品种的形成过程。这表明遗传漂变，选择和互补性等因素将遗传结构转移到一个独特的不同种群中。