Chemically induced competence followed by transformation is a commonly used technique to introduce plasmids or other DNA fragments into Escherichia coli. Depending on the genetic information it carries, the incoming DNA can be replicated as an independent entity or integrated into the host chromosome. To select for cells that incorporate the DNA, a plasmid is engineered to carry selectable markers, such as antibiotic resistance genes. Plasmid uptake provides the host cell with the ability to survive on a selective media. Today, chemically induced transformation is frequently used to clone and amplify a fragment of a gene, a whole gene or an entire DNA library. Transformation of cells with DNA is an invaluable technique that provides scientists with a way to introduce and manipulate genes.