The study investigates the mechanisms of DNA integration and recombination in yeast, focusing on the role of homologous recombination. The researchers found that DNA ends are highly recombinogenic and interact directly with homologous chromosomal sequences. Circular hybrid plasmids can integrate via a single reciprocal crossover, but at a low frequency. Restriction enzyme digestion within a region homologous to yeast chromosomal DNA significantly enhances integration efficiency. Notably, when two restriction cuts are made within the same homologous sequence, removing an internal segment of DNA, the resulting deleted-linear molecules still transform at high frequencies. Surprisingly, the integration of these gapped-linear molecules results in the replacement of the missing segment using chromosomal information, leading to a final structure identical to that obtained from circular molecules. The integration of linear and gapped-linear molecules is blocked by the rad52-1 mutation, suggesting that RAD52 may be involved in DNA repair synthesis required for these processes. The findings have implications for the isolation of integrative transformants, fine-structure mapping, and the cloning of mutations.The study investigates the mechanisms of DNA integration and recombination in yeast, focusing on the role of homologous recombination. The researchers found that DNA ends are highly recombinogenic and interact directly with homologous chromosomal sequences. Circular hybrid plasmids can integrate via a single reciprocal crossover, but at a low frequency. Restriction enzyme digestion within a region homologous to yeast chromosomal DNA significantly enhances integration efficiency. Notably, when two restriction cuts are made within the same homologous sequence, removing an internal segment of DNA, the resulting deleted-linear molecules still transform at high frequencies. Surprisingly, the integration of these gapped-linear molecules results in the replacement of the missing segment using chromosomal information, leading to a final structure identical to that obtained from circular molecules. The integration of linear and gapped-linear molecules is blocked by the rad52-1 mutation, suggesting that RAD52 may be involved in DNA repair synthesis required for these processes. The findings have implications for the isolation of integrative transformants, fine-structure mapping, and the cloning of mutations.