Megaplasmid

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Megaplasmids are large bacterial replicons that, unlike plasmids , contain an origin of replication just like chromosomal DNA . In addition to the linear chromosome , the circular chromosome and the normal plasmid, they form the fourth form in which genes can be present in prokaryotes .

Some megaplasmids appear to contain genes that are essential for cell survival. Therefore, it is difficult to decide whether a megaplasmid should be counted among the chromosomes or plasmids.