What effect does the treatment of the host cell with divalent cations have on the process of DNA entry into the bacterium?

Enhanced efficiency of DNA entry into the bacterium

The correct answer is Option (2) -Enhanced efficiency of DNA entry into the bacterium

Since DNA is a hydrophilic molecule, it cannot pass through cell membranes. To introduce recombinant DNA into bacterial cells, the cells must first be made competent to take up the DNA. In order to force bacteria to take up the plasmid, the bacterial cells must first be made ‘competent’ to take up DNA. Competency refers to the ability of bacterial cells to be transformed or take up foreign DNA. This is achieved by treating the cells with a specific concentration of a divalent cation, such as calcium which increases the efficiency with which DNA enters the bacterium through pores in its cell wall. Recombinant DNA can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42⁰C (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA.