Key issues relating to the genetic stability and preservation of cells and cell banks.

The long term maintenance of genetically stable cells is important for ensuring reproducible results and continuity in the advance of microbiology, cell biology and biotechnology. As actively growing cultures, cells are constantly at risk of changing, and the necessity for subculturing living materials increases the chances for genetic change and contamination. Many techniques are available for stabilizing living cells; the method employed must be compatible with the intended use of the culture. The most commonly utilized means of preserving living cells are by freezing to cryogenic temperatures, and freeze-drying. Master stocks are usually maintained at liquid nitrogen or comparable temperatures, while working stocks can be frozen or freeze-dried, and maintained at more economical and easily managed temperatures where possible. However, low temperature techniques may cause damage that can result in genetic change, or potential selection when only a small portion of the population survives. Therefore, a good preservation program must include a comprehensive cell characterization regimen that is applied both before and after preserving the cells to ensure that changes are detected when they do occur. Assurance of long term stability necessitates well designed safekeeping and security measures that include minimizing specimen handling through well designed inventory systems, validation and monitoring of storage temperatures, provisions for backup inventory, and training of personnel. Cell banking also requires good cataloguing and data management practices to avoid duplication and misidentification, and to ensure proper tracking of specimens and ease of access.