A. The DNA is a hydrophilic molecule. It cannot pass through cell membranes. In order to pass DNA into the bacterial cell, the bacterial cells must made ‘competent’ to take up DNA. This is done by treating the cell with a specific concentration of a divalent cation, such as calcium ions (Ca++) which increases the efficiency with which DNA can enters the bacterium through pores in its cell wall.
B. The biolistic or gene gun is a method to introduce alien DNA into the plant cells. In this method plants, cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA. Thus, the recombinant DNA is transferred into the plant cell.
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