EDVOTEK® Resources for HOSA Biotechnology Event
Bacterial Transformation and Transformation Efficiency
In nature, non-essential genes are found on small circu- lar pieces of double-stranded DNA known as plasmids . These plasmids facilitate the exchange of beneficial genes among bacteria and can replicate independently from the cell’s chromosomal DNA. In the lab, we can modify plasmids by introducing genes from various sources. When these engineered plasmids are intro- duced into bacteria, they transform the bacteria into liv- ing factories capable of producing valuable substances like medications, vitamins, and insulin, which is used to treat diabetes. Since E. coli are not naturally competent, we need to force them to take up plasmid DNA in the lab. This can be done with electricity, in a process called electropora- tion, or through physical means in a heat shock. In a heat shock transformation , the cells are treated with
calcium chloride to make them “competent”. DNA is added to the cells before they are moved quickly be- tween two very different temperatures. It is believed that the combination of calcium chloride and the rapid change in temperature changes the permeability of the cell wall and membrane, allowing DNA molecules to enter the cell. In practice, transformation is highly inefficient—only one in every 10,000 cells successfully incorporates the plasmid DNA. However, since many cells are used in a transformation experiment (about a billion cells), only a few cells must be transformed to achieve a positive outcome. We can use the data from our experiment to determine how well our transformation worked.
BACTERIAL TRANSFORMATION EXPERIMENTS:
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