Using Sperm-seq, Bell et al. sequenced the genomes of 31,228 gametes from 20 sperm donors, identifying 813,122 crossovers, 787 aneuploid chromosomes, and unexpected genomic anomalies. Avery’s results can be incorporated with earlier studies into a unified model in which the variable physical compaction of meiotic chromosomes generates interindividual and cell-to-cell variation in meiotic phenotypes such as crossover frequency and placement. Her work was published by Nature and covered by HMS news and Genomeweb.