Question
Why is it difficult for DNA to pass through cell membranes? How can E.coli cells be made competent and who developed this method?
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Answer
DNA is a hydrophillic molecule so it is difficult to cross lipid molecules of membrane.
- To make E. coli cells competent to take up DNA, they should be treated with divalent cations or calcium.
- In 1970, Mandel and Higa found that E.coli cells become competent to take up DNA when they are suspended in cold calcium chloride.
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