Transformation

1. Transformation is the genetic alteration of a cell resulting from the introduction, 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 bacteria for transformation, normally cannot take up plasmid DNA. However, exposure of the cells to divalent cations such as CaCl2 makes them more permeable to DNA. This process is relatively inefficient; electric pulses can increase the incorporation efficiency much more. An example of transformation is bT cotton, which incorporates BT genes which afford cotton plants a degree of protection against certain insect pests.
2. Transformation is also the process by which normal cells are converted into cells that will continue to divide without limit. Normal cells can divide only a certain number of times before they will stop dividing. Cells that have been transformed no longer have such a limit (for example, cancer cells) are able to grow and divide potentially forever.

In mathematics, "transformation" refers to a variety of different operations that can be performed using linear algebra. For example, in 3D computer graphics, the operations of moving, scaling, or rotating a 3D model are commonly called transformations.