What are the necessary components of a plasmid?
- Origin of replication(ori):a required sequence or element on the plasmid for its replication inside the host.Also called as the replicon.
- Selectable Marker: a required element for cloning to select a host,which carries the DNA construct.The only host cell growing in the growth medium containing a particular selective agent has the DNA construct with a selective marker inside the cell.For an example,selectable markers in the DNA construct often contain antibiotic resistance gene .A transformed host has the antibiotic resistance gene on the DNA construct,therefore it can grow in the medium with that particular antibiotic.On the other hand, the host cell without the DNA construct can't survive in the selective medium.
- Multiple Cloning Site:an element on the plasmid fragment which contains restriction enzyme site to allow DNA insertion.
- Promoter Region: a region which drives the protein expression of the cloned DNA.It allows gene transcription .RNA polymerase binds to promoter region.
- Protein Tag:a particular sequence which produces a protein with specific function ,and it is usually attached to the recombinant protein. Example: luciferase/GFP to monitor or quantify the protein.
- Poly-adenylation signal:- an element containing poly-A which is important to produce a protein.