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Transformation has two meaning in molecular biological:

  • Transformation is the genetic alteration of a cell due to the uptake and expression of foreign DNA. This is a common technique in molecular biology. The effect was first demonstrated in 1944 by Avery, Macleod, and McCarty, who first demonstrated gene transfer in Streptococus pneumoniae. E.coli, which is one of the most commonly used bacteriums for transformation, normally cannot uptake plasmid DNA. Exposure of cells to divalent cations such as CaCl2 makes them more permeable to DNA. This process is relatively inefficient; electric pulses can increase the incorporation efficency greatly.
  • Transformation is also the process by which normal cells are converted into cells that grown continuously.