The transmission of DNA from parents to offspring involves shuffling that generates new genetic combinations. Recombination helps ensure the faithful segregation of chromosomes when organisms generate eggs or sperm. Despite this vital function, the rate at which recombination happens varies along chromosomes and among individuals. By revealing the dynamics of recombination rate change over time, we are demonstrating how a fundamental evolutionary force itself evolves.
Sex Differences in the Evolution of Recombination
Females and males often recombine at different rates. We demonstrated that the number of crossovers along the genome shows higher genetic variation in male house mice than in female house mice from the same set of strains. Our results suggest that recombination responds to distinct evolutionary pressures in the sexes. We are incorporating this finding into new models for the evolution of recombination.
Genetics and Cellular Determinants of Recombination Evolution
Recombination is enabled by proteins that help “zip” matching chromosomes inherited from mother and father. We mapped differences between wild house mice in this synaptonemal complex. Some of the resulting genomic regions also affect the number of crossovers along the genome. These findings indicate that recombination rate can evolve via modification of the synaptonemal complex. We hope to expand our genetic examination of the cellular causes of recombination evolution to include other features, such as crossover interference.
Molecular Evolution of Genes that Control Recombination
Crossovers are the culmination of a finely orchestrated series of steps and intermediates. We discovered that genes that stabilize chromosome pairing and participate in the decision about whether DNA breaks are resolved as crossovers evolved rapidly across mammals. At one gene, the rate of evolution correlates with the number of crossovers, making this gene a candidate for the evolution of recombination. We aim to exploit this pathway perspective to elucidate the molecular changes responsible for changes in recombination.