Intrachromosomal recombination between the rDNA repeats can produce extrachromosomal rDNA circles (ERCs) that have been postulated to induce senescence in aging mothers by an undefined mechanism [39]. Each repeat contains an origin of DNA replication, allowing ERCs to replicate independently, but lacks a centromeric sequence to ensure equal partitioning of ERCs between mother and daughter cells during mitosis [39]–[40]. Consequently, ERCs preferentially accumulate within aging mother cells. It has been suggested recently that ERCs can influence rDNA array stability in haploid cells [41]. Given these findings, we explored whether ERC levels play a role in age-associated LOH in diploid cells.
