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Biotechnology: Principles and Processes — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYBiotechnology: Principles and Processes3 Marks
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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