Complex sentence: For reason of ease and convenience, cloning is often performed using "E. coli", the cloning vectors used therefore often have elements necessary for their propagation and maintenance in "E. coli" such as a functional origin of replication (ori).
Split into simpler sentences: For reason of ease and convenience, cloning is often performed using "E. coli". Thus, the cloning vectors used often have elements necessary for their propagation and maintenance in "E. coli" such as a functional origin of replication (ori).