Correlation between suppressed meiotic recombination and the lack of DNA strand-breaks in the rRNA genes of Saccharomyces cerevisiae.

We have examined whether the suppressed homologous meiotic recombination within the rDNA of S. cerevisiae is reflected by a lack of possibly recombination-initiating strand-breaks in this part of the genome. Our findings indicate that bulk DNA in the ds-break repair deficient mutant rad52/rad52 accumulates a limited number of both ss- and ds-breaks during meiosis as compared to a RAD+/rad52 heterozygote. The rDNA-containing chromosome is however protected against these breaks, and thus this may be an explanation for the suppression of recombination in the rDNA. The fact that ds-breaks seem to be involved gives indirect support to the ds-break-repair model for recombination.