Question

The correct sequence of making a cell competent is

• A. Treatment with divalent cations, incubation of cells with recombinant DNA on ice, heat shock (${42}^0$C) again placing on ice.
• B. Heat shock (${42}^0$C), incubation of cells with recombinant DNA on ice treatment with divalent cations placing on ice.
• C. Treatment with divalent cations, placing on ice incubation of cells with recombinant DNA on ice heat shock (${42}^0$C).
• D. Incubation of cells with recombinant DNA on ice, heat shock (${42}^0$C) treatment with divalent cations placing on ice

Answer 1

The correct option is A Treatment with divalent cations, incubation of cells with recombinant DNA on ice, heat shock (${42}^0$C) again placing on ice.

• In order to force a bacterium to take up the plasmid, the bacterial cells have to be made competent.
• This is done by treating them with a specific concentration of divalent cations such as calcium which increases the efficiency with which the DNA molecule enters the bacteria through pores in its cell wall.
• Recombinant DNA then forced into such cells by incubating the cells with recombinant DNA on ice followed by placing them immediately at heat shock and then again into ice.
• This enables the bacteria to take up the recombinant DNA.

So, the correct option is 'Option A'.