Explain the application of biotechnology in producing Bt cotton.

OR

Unless the vector and source DNA are cut, fragments separated and joined, the desired recombinant vector molecule cannot be created.

(a) How are the desirable DNA sequences cut ?

(b) Explain the technique used to separate the cut fragments.

(c) How are the resultant fragments joined to the vector DNA molecule ?

Biotechnology has been used to widely produce Bt cotton. Bt cotton is a genetically modified organism or genetically modified pest resistant plant cotton variety, which produces an insecticide to combat bollworm.

a. The Bt toxin gene has been cloned from the bacteria and expressed in plants.

b. Bt toxin gene forms protein crystals which contain a toxic insecticidal protein.

c. Bt toxin protein exists in inactive protoxin form in the host.

d. It gets activated when the insect ingests the inactive toxin.

e. The alkaline pH of the gut of the insect which solubilises the crystals causing the death of the insect.Formation of fruit in banana occurs without fertilization. Thus, it is a good example of parthenocarpy.

OR

a. Restrictions enzymes are used to cut the desirable sequences in DNA. Restriction enzymes like EcoRI cut at specific palindromic sequences. The Cut ends overhang as sticky ends in the medium.

b. The techniques used to separate the cut fragments from the medium is called gel electrophoresis.The steps are as follows:

i. The fragments are fed in well made up of agarose gel.

ii. Electric current is run through a gel containing the DNA fragments.

iii. The fragments travel through the gel in different directions or at different speeds, on the basis of the of size or charge, and get separated. Negatively changed fragments move towards the anode and the smaller sized fragments move at a faster pace.

c. The resultant fragments are joined to the vector DNA molecule by adding them to the medium containing the vector DNA. The sticky ends facilitate the action of the ligase enzyme and join the source DNA to the vector.