DONATION OF INFORMATION TO THE UNBROKEN CHROMOSOME IN DOUBLE-STRAND BREAK REPAIR

We have used transformation of yeast with linearized plasmids to study the transfer of information to the unbroken chromosome during double- strand break repair. Using a strain which carried the wild-type HIS3 a llele, and a linearized plasmid which carried a mutant his3 allele, we have obtained His- transformants. In these, double-strand break repai r has resulted in precise transfer of genetic information from the pla smid to the chromosome. Such repair events, we suggest, are gene conve rsions which entail the formation of heteroduplex DNA on the (unbroken ) chromosome. If this suggestion is correct, our results reflect the s patial distribution of such heteroduplex DNA. Transfer of information from the plasmid to the chromosome was obtained at a maximal frequency of 1.5% of the repair events, and showed a dependence with distance. Transformation to His- was also obtained with a 2-kbp insertion and wi th a deletion of 200 bp. The latter results suggest that gene conversi on of large heterologies can occur via repair of a heteroduplex DNA in termediate.