Arrange the following steps involved in transformation of bacteria in…

The correct answer is Option (2) → (B), (A), (C), (E), (D)

(B) Treatment with divalent cations — first. DNA cannot pass through the cell membrane on its own, because it is a hydrophilic molecule. The cells are first made competent by treating them with a divalent cation such as calcium, which helps DNA enter through pores in the cell wall.

(A) Incubation of rDNA with bacterial cell on ice — second. The recombinant DNA is mixed with the competent cells and the two are kept on ice together.

(C) Heat shock treatment — third. The cells are placed briefly at 42°C. This sudden heat lets the rDNA enter the bacteria.

(E) Placed them again on ice — fourth. Right after the heat shock, the cells are put back on ice.

(D) Selection on antibiotic-containing agar plate — last. Only the cells that took up the rDNA carry its antibiotic resistance gene. They alone grow on the antibiotic plate, so the transformants are picked out.

NCERT Extract:
Competent Host (For Transformation with Recombinant DNA) – “… In order to force bacteria to take up the plasmid, the bacterial cells must first be made ‘competent’ to take up DNA. This is done by treating them 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 42°C (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA.”
Insertion of Recombinant DNA into the Host Cell/Organism – “… If we spread the transformed cells on agar plates containing ampicillin, only transformants will grow, untransformed recipient cells will die.”