The breakdown of genomic ancestry blocks in hybrid lineages given a finite number of recombination sites

When a lineage originates from hybridization genomic blocks of contiguous ancestry from different ancestors are fragmented through genetic recombination. The resulting blocks are delineated by so called “junctions”, which accumulate with every generation that passes. Modeling the accumulation of ancestry block junctions can elucidate processes and timeframes of genomic admixture. Previous models have not addressed ancestry block dynamics for chromosomes that consist of a finite number of recombination sites. However, genomic data typically consist of informative markers that are interspersed with fragments for which no ancestry information is available. Hence, repeated recombination events may occur between markers, effectively removing existing junctions. Here, we present an analytical treatment of the dynamics of the mean number of junctions over time, taking into account the number of recombination sites per chromosome, population size, genetic map length and the frequency of the anc...当一个谱系（lineage）源自杂交事件时，来自不同祖先的连续起源基因组片段会通过遗传重组（genetic recombination）发生断裂。由此产生的片段以所谓的“连接点（junction）”为边界，且这些连接点的数量会随每一代的传递不断累积。对祖先起源片段连接点的累积过程进行建模，能够阐明基因组混合的具体过程与时间尺度。既往模型尚未针对由有限数量重组位点构成的染色体开展祖先起源片段动力学特征的研究。然而，基因组数据通常包含交错分布的信息性遗传标记与大量无祖先起源信息的基因组片段，因此标记之间可能发生重复重组事件，进而有效清除已存在的连接点。本文针对平均连接点数目随时间变化的动力学过程开展解析分析，综合考量了每条染色体的重组位点数、种群大小、遗传图谱长度以及祖先相关频率（原文未完整给出）。