Volume 228, Issue 1, September 2024

Ancestral Recombination Graphs (ARGs) describe the complex web of genetic ancestry that results from individuals inheriting parts of their genomes through different routes. Classical methods of describing ARGs focus on evolutionary events, but this approach is out of step with some modern developments and cannot describe their outputs. The authors provide a simple alternative formulation that generalises this classical view show how it leads to efficient software.

Meiotic recombination involves formation of programmed DNA double strand breaks followed by 5’ to 3’ single strand specific resection by nucleases including Exo1. The authors find that the activity of budding yeast Exo1 is downregulated during meiotic recombination by the master meiotic kinase Mek1. The mechanism of downregulation of Exo1 by Mek1 in meiosis does not depend on the same phospho-sites as those used by the mitotic kinase Rad53, a relative of Mek1 that downregulates Exo1 in mitosis.

Over the past decade, advances in ancient DNA research have provided crucial insights into population demographic history. Ancient DNA has been shifting towards studying the more recent past, referred to as archaeogenetics. The authors research evaluates the effectiveness and limitations of two widely used methods, the f₃-statistic and qpAdm, in reconstructing admixture histories under complex historical population dynamics. Their findings highlight the challenges in accurately reconstructing complex genetic histories and provide guidelines for more reliable inference heuristics in archaeogenetic analyses.

Genes encoding ribosomal RNA are highly conserved and present as large tandem repeat arrays, called rDNA, in most eukaryotes. rDNA repeat unit size is also conserved across most eukaryotes, but is dramatically larger in mammals. Here the authors locate the expansion of rDNA size to the base of the mammals, with other amniote lineages having normal rDNA unit sizes. Unexpectedly, they find that large mammalian rDNA size has been maintained despite substantial sequence turnover, suggesting a previously-unrecognized constraint on rDNA length.