Any DNA molecule formed by joining DNA segments from different sources. Small, circular, extrachromosomal DNA molecules.
Plasmids frequently carry genes for antibiotic resistance.
While antibiotic resistance is becoming an increasingly important problem medically, it is a useful marker in Recombinant DNA technology. Such markers, along with the small size and potentially high copy number, make plasmids indispensible tools in Molecular Biology. This plasmid map has 3 marked regions on it. The arrows denote the direction the genes are transcribed. Any DNA not recognized as self is digested into smaller pieces by the Restriction Enzymes.