THE CHROMOSOME BIAS OF MISINCORPORATIONS DURING DOUBLE-STRAND BREAK REPAIR IS NOT ALTERED IN MISMATCH REPAIR-DEFECTIVE STRAINS OF SACCHAROMYCES-CEREVISIAE

Recombinational repair of a site-specific, double-strand DNA break (DS B) results in increased reversion frequency for nearby mutations. Alth ough some models for DSB repair predict that newly synthesized DNA wil l be inherited equally by both the originally broken chromosome and th e chromosome that served as a template, the DNA synthesis errors are a lmost exclusively found on the chromosome that had the original DSB (i ntroduced by the HO endonuclease). To determine whether mismatch repai r acts on the template chromosome in a directed fashion to restore mis matches to the initial sequence, these experiments were repeated in mi smatch repair-defective (pms1, mlh1, and msh2) backgrounds. The result s suggest that mismatch repair is not responsible for the observed bia s.