A COMPARISON OF POSTMIGRATION AND MIGRATION-COUPLED MISMATCH CORRECTION MECHANISMS FOR BRANCH MIGRATION-MEDIATED GENE CONVERSION

Brian Seed ¹

¹ Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114

We examine several models for nonreciprocal recombination based on the formation of heteroduplex DNA by bidirectional branch migration. We show that the consistency of genetic maps resulting from postmigration mismatch correction is disrupted by the presence of a favored site for initiation of strand exchange, with local inversion of the genetic and physical maps a predicted consequence. We also examine models that allow mismatch correction to take place concurrently with the process of strand exchange and show that the genetic maps resulting from such migration-coupled conversions are substantially free of the anomalies expected of postmigration conversions.