High-resolution mapping of crossovers reveals extensive variation in fine-scale recombination patterns among humans.

Recombination plays a crucial role in meiosis, ensuring the proper segregation of chromosomes. Recent linkage disequilibrium (LD) and sperm-typing studies suggest that recombination rates vary tremendously across the human genome, with most events occurring in narrow "hotspots." To examine variation in fine-scale recombination patterns among individuals, we used dense, genome-wide single-nucleotide polymorphism data collected in nuclear families to localize crossovers with high spatial resolution. This analysis revealed that overall recombination hotspot usage is similar in males and females, with individual hotspots often active in both sexes. Across the genome, roughly 60% of crossovers occurred in hotspots inferred from LD studies. Notably, however, we found extensive and heritable variation among both males and females in the proportion of crossovers occurring in these hotspots.