Plasmids are DNA molecules that exist outside of chromosomes.
They are small, spherical, and capable of self-replication.
Some eukaryotes, such as yeast and plants, have plasmids.
Because of their ability to multiply independently, plasmids are utilized as cloning vectors in recombinant DNA technology for transferring and altering genes.
Copy number in plasmids:
A plasmid's copy number is the number of molecules that can be found in a single bacterial cell.
The number of copies and size of a plasmid are particularly important when it comes to cloning.
A few plasmids, particularly the larger ones, are rigorous, requiring only 1-2 copies per cell.