An expression vector is a relatively small DNA molecule that can be used to carry a specific gene into a target cell. Once the expression vector is inside the cell, the protein that is coded for by the gene is produced by the normal transcription and translation processes of the host cell. Expression vectors are used for molecular biology techniques such as site-directed mutagenesis. In general, DNA vectors that are used in many molecular biology gene cloning experiments need not result in the expression of a protein. Expression vectors are often specifically designed to contain non-protein-coding sequences that act as enhancer and promoter regions and allow efficient transcription of the gene that is carried on the expression vector. Expression vectors are basic tools for biotechnology and the production of proteins such as insulin that are important for medical treatments of specific diseases like diabetes.