The ability to transfer genes from one cell to another and maintain them in new cells is called transformation. Plasmids are used for transferring DNA into bacteria. A common method for doing this is using a bacteriophage, such as lambda phage, which attaches itself to the bacterial cell wall and injects the plasmid into the cell. This process may cause mutations and deletions in the plasmid, which makes it impossible to grow out clones containing the desired mutation. However, the presence of an antibiotic resistance gene allows the transformed cells to survive exposure to antibiotics.