Cloning vectors and expression vectors are two types of vectors, used in recombinant DNA technology to transfer foreign DNA chain segments into a target cell. Both cloning and expression vectors comprise replication origin, multiple cloning sites, and selectable marker genes in their vector sequences. Both cloning and expression vectors are self-replicative due to the presence of a replication origin. Cloning vectors can be either plasmids, cosmids, or bacteriophages. The main difference between a cloning vector and an expression vector is that a cloning vector is used to transfer foreign DNA chain segments into a host cell, whereas an expression vector is a type of cloning vector, which contains suitable expression signals, promoter，ribosome-binding site, stop code with maximal gene expression.