One interesting yeast plasmid is called the 2u circle. The 2u circle is a 6.3 kb circular, extrachromosomal element found in the nucleus of most Saccharomyces cerevisiae strains. The 2u circle doesn't give cells that carry it any apparent selective advantage, but it is stably maintained at about 50 to 100 copies per haploid genome of the yeast cells. Like the host chromosomes, the 2u circle is coated with nucleosomes and replication is initiated by host replication enzymes once per cell cycle. The origin of bidirectional DNA replication is initiated at a specific site on the plasmid called an ARS sequence