Question

What are the elements of a cloning vector?

What additional elements does an expression vector contain? What is the purpose of each of these elements?

Answer 1

An origin of replication, a selectable marker, a multiple cloning site, a reporter gene are the elements of a cloning vector.

A promoter, a ribosomal binding site and start codon, a termination codon, a transcription termination sequence, protein tags, elements for transformation like vir genes, integrase are the additional elements that an expression vector contain.

Origin of replication is necessary for the propagation and maintenance of the vector. Selectable marker is necessary for the selection of positively transformed cells. A gene can be conveniently inserted into the vector or removed from it in a multiple cloning site. Reporter genes are used to facilitate the screening of successful clones. A promoter, ribosomal binding site and start codon, termination codon, transcription termination sequence are the elements necessary for the expression of a cloned target gene. Protein tags are necessary to purify the expressed protein. Some expression vectors may contain elements for transformation like the vir genes for plant transformation, and integrase sites for chromosomal insertion.