Meiotic recombination shapes precision of pedigree- and marker-based estimates of inbreeding

The proportion of an individual’s genome that is identical-by-descent (GWIBD) can be estimated from pedigrees (inbreeding coefficient “Pedigree F”) or molecular markers (“Marker F”), but both estimators come with error. Assuming unrelated pedigree founders, Pedigree F is the expected proportion of GWIBD given a specific inbreeding constellation. Meiotic recombination introduces variation around that expectation (Mendelian noise) and related pedigree founders systematically bias Pedigree F downwards. Marker F is an estimate of the actual proportion of GWIBD but it suffers from the sampling error of markers plus the error that occurs when a marker is homozygous without reflecting common ancestry (identical-by-state). We here show via simulation of a zebra finch and a human linkage map that three aspects of meiotic recombination (independent assortment of chromosomes, number of cross-overs and their distribution along chromosomes) contribute to variation in GWIBD and thus the precision of ...个体基因组中同源同缘（identical-by-descent，GWIBD）片段的占比，可通过系谱数据估算对应近交系数系谱F（Pedigree F），或通过分子标记估算对应标记F（Marker F），但两种估算方法均存在误差。在假定系谱奠基者无亲缘关系的前提下，系谱F为特定近交构型下同源同缘片段占比的理论期望值。减数分裂重组会使实际占比围绕该理论期望值产生波动，即孟德尔噪音；若系谱奠基者本身存在亲缘关系，则会使系谱F的估算值系统性偏低。标记F是对同源同缘片段实际占比的直接估算，但该估算会受到标记抽样误差的影响，同时还会因标记处于纯合状态却未反映共同祖先（即同态，identical-by-state）而引入额外误差。本研究通过斑胸草雀（zebra finch）与人类连锁图谱（linkage map）的模拟实验证实，减数分裂重组的三个关键特征——染色体独立分配、交换事件数量及其在染色体上的分布——均会导致同源同缘片段占比产生波动，进而影响……