Molecular Genetics

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One way of physically introducing DNA into a cell is electroporation.

• The diagram shows an electrical circuit diagram for a simple electroporation device.
• A cell suspension, such as of plant protoplasts, is placed in the cuvette. A solution of DNA fragments containing the gene of interest is added. For example, the DNA could include a reporter gene such as that for chloramphenicol acetyltransferase (CAT).
• The capacitor is charged by closing the right-hand switch. When the capacitor has been charged, the direct current pulse is discharged in the cuvette suspension by closing the left-hand switch.
• The DC pulse is thought both to disrupt temporarily the membrane and to electrophorese DNA into cells.
• The cells are put in culture and assayed after various times (24 to 48 h) for the amount of CAT activity (see right).

Further Information

• The highest levels of enzyme activity are not maintained with time in culture; the enzyme is expressed transiently.
• Transient expression can be used to measure the relative activities of related gene constructs (to locate promoters, factor binding sites, etc.). For this purpose, the use of reporter genes is often preferred.
• In a small percentage of the cells, the introduced DNA becomes integrated into the host chromosomes or established in the cell as an episome. Electroporation is thus also a method used in transformation.
• Human, other animal, yeast and bacterial cells are also targets of electroporation.
• Electroporation is but one way of putting DNA into living cells.