Askjagden's Guide to Biology: Cell Transformation
Transformation is when a cell takes DNA from outside from the cell. This external DNA becomes a part of the cell's DNA. During British scientist Frederick Griffith's experiment, a mouse ded from pneumonia after being injected by heat-killed bacteria and disease-causing bacteria. This resulted from transformation.
Here's how cell transformation works. The foreign DNA is first joined to a plasmid, or a circular DNA molecule. The plasmid has a genetic marker, which is a gene that makes it possible to distinguish bacteria that carry the plasmid from ones that don't. If transformation is successful, the recombinant DNA is integrated into one of the chromosomes of the cell.
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