Variation in actual relationship as a consequence of Mendelian sampling and linkage.
Variation in actual relationship as a consequence of Mendelian sampling and linkage.
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DOI：
10.1017/s0016672310000480
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发表时间：
2011-02
影响因子：
1.5
通讯作者：
Weir, B. S.
中科院分区：
文献类型：
--
作者：
Hill, W. G.;Weir, B. S.
尽管可以从血统中获得预期的亲属关系或共享基因组的比例，但实际数量会因孟德尔采样而产生偏差，并取决于染色体的数量和图谱长度。先前已发布了一些特定类型亲属的实际关系方差的公式，但没有适用于非近交个体的通用公式。我们在这里提供了一个统一的框架，可以轻松计算远亲的方差，例如，显示曾祖父母-曾孙、曾叔叔-曾侄子、同父异母的叔叔-侄子和堂兄弟姐妹的共享方差如何不同，即使他们具有相同的预期关系。结果被扩展以包括性别之间图谱长度的差异、雄性中没有重组和性别连锁。我们得出了共享比例的偏差大小，表明关系越远，偏差就越大。实际关系变化获得的结果直接适用于实际近交的变化，因为两者都是基因组共源性的函数，并且我们展示了如何划分家庭之间和内部实际近交的变化。尽管实际关系的方差随着个体的距离越来越远而下降，但其变异系数却上升，因此，由于偏度而加剧，区分不同的谱系关系与共享基因组的实际部分变得越来越困难。
Although the expected relationship or proportion of genome shared by pairs of relatives can be obtained from their pedigrees, the actual quantities deviate as a consequence of Mendelian sampling and depend on the number of chromosomes and map length. Formulae have been published previously for the variance of actual relationship for a number of specific types of relatives but no general formula for non-inbred individuals is available. We provide here a unified framework that enables the variances for distant relatives to be easily computed, showing, for example, how the variance of sharing for great grandparent–great grandchild, great uncle–great nephew, half uncle–nephew and first cousins differ, even though they have the same expected relationship. Results are extended in order to include differences in map length between sexes, no recombination in males and sex linkage. We derive the magnitude of skew in the proportion shared, showing the skew becomes increasingly large the more distant the relationship. The results obtained for variation in actual relationship apply directly to the variation in actual inbreeding as both are functions of genomic coancestry, and we show how to partition the variation in actual inbreeding between and within families. Although the variance of actual relationship falls as individuals become more distant, its coefficient of variation rises, and so, exacerbated by the skewness, it becomes increasingly difficult to distinguish different pedigree relationships from the actual fraction of the genome shared.