Definition: Infection of a bacterium or cell with DNA or RNA isolated from a bacteriophage or from an animal or a plant virus, resulting in replication of the complete virus.

Explanation: Introducing DNA into eukaryotic cells, such as animal cells, is called transfection. Transfection typically involves opening transient "holes" or gates in cells to allow the entry of extracellular molecules, typically supercoiled plasmid DNA, but also siRNA, among others. Several different transfection techniques are available, including calcium phosphate transfection, lipofection, electroporation, heat shock, and proprietary transfection reagents such as Fugene. The choice of transfection methods differs upon cell sensitivity to the conditions, and the amount of work and cost involved. Typically, transfection of bacteria is done by heat shock or electroporation, which are quick, cheap and easy procedures to carry out, as bacteria are easy to grow and multiply rapidly, even from a small portion of survivors. For eukaryotic cells, lipid- cation based transfection is more typically used, as the cells are more sensitive. The drawback is that this is costlier, and requires more work, which is typical of eukaryotic cell culture procedures in general. DNA can also be introduced into cells using viruses as a carrier. In such cases, the technique is called viral transduction, and the cells are said to be transduced.

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