Extrachromosomal rDNA circles (ERC) are self replicating circles of ribosomal DNA found in some strains of yeast and thought to contribute to their aging.
The ERC accumulate in the mother cell during the budding process.
They are a type of Extrachromosomal Circular DNA (eccDNA), a type of Extrachromosomal DNA.
References
Extrachromosomal rDNA circle Wikipedia(Text) CC BY-SA