(a) Why must a cell be made 'competent'  in biotechnology experiments ? How does
calcium ion help in doing so ?

(b) State the role of 'biolistic gun' in biotechnology experiments.

(A) It is necessary to make cell competent in order to enhance the efficiency of cell to take up foreign DNA easily.
When the cell is treated with a specific solution of divalent cation calcium. It increases the efficiency of the cell to take up the foreign DNA through the pores in the cell wall.
(B) Biolistics and Gene gun is one of the methods to transfer the foreign DNA into the host.
In this method the suitable plant cells are bombarded with high-velocity micro-particles 
of gold & tungsten coated with DNA.