(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) State the importance of gel electrophoresis in biotechnology.
(2) Explain the principle on which this technique works.
(3) Mention why ethidium bromide is used in this technique.
OR
(b) (i) How was Bt cotton, the genetically modified crop, has greatly helped the cotton farmers to increase their crop yield?
(ii) Describe the mechanism that leads to the death of bollworms feeding on Bt cotton plants.