The drift-barrier hypothesis states that random genetic drift constrains the refinement of a phenotype under natural selection. The influence of effective population size and the genome-wide deleterious mutation rate were studied theoretically, and an inverse relationship between mutation rate and genome size has been observed for many species. However, the effect of the recessive gene count, an important feature of the genomic architecture, is unknown. In a Wright-Fisher model, we studied the mutation burden for a growing number of N completely recessive and lethal disease genes. Diploid individuals are represented with a binary $2 \times N$ matrix denoting wild-type and mutated alleles. Analytic results for specific cases were complemented by simulations across a broad parameter regime for gene count, mutation and recombination rates. Simulations revealed transitions to higher mutation burden and prevalence within a few generations that were linked to the extinction of the wild-type haplotype (least-loaded class). This metastability, that is, phases of quasi-equilibrium with intermittent transitions, persists over $100\,000$ generations. The drift-barrier hypothesis is confirmed by a high mutation burden resulting in population collapse. Simulations showed the emergence of mutually exclusive haplotypes for a mutation rate above 0.02 lethal equivalents per generation for a genomic architecture and population size representing complex multicellular organisms such as humans. In such systems, recombination proves pivotal, preventing population collapse and maintaining a mutation burden below 10. This study advances our understanding of gene pool stability, and particularly the role of the number of recessive disorders. Insights into Muller`s ratchet dynamics are provided, and the essential role of recombination in curbing mutation burden and stabilizing the gene pool is demonstrated.
Analytical results on the Muller's ratchet effect in growing populations
Fontanari等人介绍了[Phys. Rev. Lett. 91，218101（2003）]的一个模型，用于研究穆勒的棘轮现象在不断增长的无性种群。他们研究了两种情况，包括或不包括每个新生儿的死亡概率，但只能在无衰变的情况下找到解析（递归）表达式。在本文中，一个分支过程的形式主义是用来找到recorrence方程，除了确认有趣的效果，他们的模拟显示，推广的分析结果的原始文件。
