(a) (i) Why should a cell be made competent to take up an alien DNA? How can a bacterial cell be made competent using calcium ions? Explain. (ii) (1)…

• DNA is a hydrophilic molecule and cannot pass through the cell membrane.

• A bacterial cell is made competent by treating the bacterial cell with a specific

concentration of a divalent cation such as calcium, which increases efficiency with which the DNA enters through pores in its cell wall/This creates certain transient pores in its cell and increases the efficiency of the cell to take up DNA.

Separation of DNA fragments .

DNA fragments are negatively charged molecules, they can be separated according to their size by forcing them to move toward the anode under an electric field through agarose gel.

To stain the DNA to visualize by exposure to UV radiation.

Specific Bt toxin gene cry IAc/cry II Ab, isolated from Bacillus thuringiensis

bacteria and incorporated into the cotton plant to provide resistance to bollworm.

Bacillus thuringiensis forms toxic insecticidal protein or Bt toxin protein during

a particular growth phase, Bt toxin protein exist as inactive pro-toxin, on ingestion by the bollworm inactive toxin is converted into active form due to alkaline pH of the gut, activated toxin binds to the surface of the mid-gut epithelial cells, create pores and causes cell swelling, lysis and death of the insect.