The genomic proportion that two relatives share identically by descent—their genetic relatedness—can vary depending on the history of recombination and segregation in their pedigree. This variation is important in many applications of genetics, including pedigree-based estimation of the genetic variance and heritability of traits, and estimation of pedigree relationships from sequence data. Here, we calculate the variance of genetic relatedness for general pedigree relationships, making no assumptions about the recombination process. For the specific relationships of grandparent-grandoffspring and siblings, the variance of genetic relatedness is a simple decreasing function of r̄, the average proportion of locus pairs that recombine in meiosis. For general pedigree relationships, the variance of genetic relatedness is likewise the average of some function of pairwise recombination rates. Therefore, features of the aggregate recombination process that affect r̄ and analogs also affect variance in genetic relatedness. Such features include the number of chromosomes and heterogeneity in their size, and the number of crossovers and their location along chromosomes. Our calculations help to explain several recent observations about variance in genetic relatedness, including that it is reduced by crossover interference (which is known to increase r̄). Our methods further allow us to calculate the neutral variance of ancestry among F2s in a hybrid cross, enabling precise statistical inference in F2-based tests for various kinds of selection.

中文翻译：

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遗传相关性的变异取决于聚集重组过程

两个亲戚在血统上共享相同的基因组比例（他们的遗传亲缘关系）可能会有所不同，这取决于他们血统中的重组和分离史。这种变异在遗传学的许多应用中都很重要，包括基于谱系的遗传变异和性状遗传估计，以及从序列数据估计谱系关系。在这里，我们计算一般谱系关系的遗传相关性方差，而无需对重组过程进行任何假设。对于祖父母-后代与兄弟姐妹的特定关系，遗传相关性的方差是r̄的简单递减函数，是减数分裂中重组的基因座对的平均比例。对于一般的谱系关系，遗传相关性的方差同样是配对重组率某些函数的平均值。因此，影响r 1和类似物的聚集重组过程的特征也影响遗传相关性的差异。这些特征包括染色体的数目和大小的异质性，交叉的数目及其在染色体上的位置。我们的计算有助于解释有关遗传相关性方差的最新观察结果，包括交叉干扰会减少这种变化（已知会增加r̄）。我们的方法还使我们能够计算混合杂交中F2之间的祖先中性方差，从而可以在基于F2的测试中进行各种选择时进行精确的统计推断。