Transformation Of Bacteria

The transformation of bacteria using recombinant DNA (rDNA) involves several key steps, each critical for the successful uptake and expression of new genetic material. Here's a detailed breakdown of the correct sequence:

1. Treatment with divalent cations (B): Initially, bacteria are treated with divalent cations like calcium or magnesium. This treatment increases the permeability of the bacterial cell membrane, making it more receptive to the acceptance of foreign DNA.
2. Incubation of rDNA with bacterial cell on ice (A): The rDNA is mixed with the treated bacterial cells and incubated on ice. This step allows the DNA to approach the bacterial cells in a less active environment, facilitating interaction.
3. Heat shock treatment (C): The mixture is then subjected to a heat shock, a rapid increase in temperature which temporarily opens up the pores in the bacterial membrane, allowing the rDNA to enter the cell.
4. Placed them again on ice (E): Post heat shock, the cells are placed back on ice to stabilize the membrane and enable the cells to recover, now housing the rDNA.
5. Selection on antibiotic containing agar plate (D): Finally, the transformed bacteria are spread onto agar plates containing an antibiotic. Only bacteria that have successfully incorporated the rDNA, which includes a resistance gene, will survive and grow in this medium, allowing for selection of transformed colonies.

Thus, the correct sequence is: (B), (A), (C), (E), (D).