Vector (molecular biology)

In molecular cloning, a vector is any particle (e.g., plasmids, cosmids, Lambda phages) used as a vehicle to artificially carry a foreign nucleic sequence – usually DNA – into another cell, where it can be replicated and/or expressed.

[2] Common to all engineered vectors are an origin of replication, a multicloning site, and a selectable marker.

These plasmid are generally non-conjugative but may have many more features, notably a "multiple cloning site" where multiple restriction enzyme cleavage sites allow for the insertion of a transgene insert.

However, because viral vectors frequently lack infectious sequences, they require helper viruses or packaging lines for large-scale transfection.

For example, retroviruses leaves a characteristic retroviral integration pattern after insertion that is detectable and indicates that the viral vector has incorporated into the host genome.

Three structural necessities of an artificial chromosome include an origin of replication, a centromere, and telomeric end sequences.

[11] A larger number of mRNAs would express a greater amount of protein, and how many copies of mRNA are generated depends on the promoter used in the vector.

Expression in different host organism would require different elements, although they share similar requirements, for example a promoter for initiation of transcription, a ribosomal binding site for translation initiation, and termination signals.