Why and how can bacteria be made 'competent'?

• DNA is a hydrophilic molecule and it cannot pass through the cell membrane hence the bacterial cell must be made competent to take up DNA. • The bacterial cells can be treated with a specific concentration of divalent cation Ca2+ this increases the efficiency with which DNA enters the bacterium through the pores in the cell wall , followed by placing the cells with recombinant DNA on ice followed by placing them briefly at 420C (heat shock) and then putting them back on ice.