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12th Biology 2012 Set1 Outside Delhi Board Paper Solution

Question 27

(a) Tobacco plants are damaged severely when infested with Meloidegyne incognitia. Name and explain the strategy that is adopted to stop this infestation.
(b) Name the vector used for introducing the nematode specific gene in tobacco plant.

Answer
(a) RNAi (RNA Interference) is the method adopted to develop nematode resistance in tobacco plant. It involves the following steps:
 
(i) Disease causing gene was identified and isolated from the nematode Meloidegyne incognitia and is incorporated into the genome of tobacco plant with the help of a suitable vector.
 
(ii) It is introduced in tobacco plant in such a way that both sense and anti-sense mRNA is produced. These RNAs being complementary get paired to from a double stranded RNA.
 
(iii) This double stranded RNA induces RNAi in the tobacco plants which neutralize the mRNA of the nematode during actual infection. Thus nematode is unable to live such as transgenic host and therefore the tobacco plant become resistant to the pest.
 
(b) The vector used for introducing the nematode specific gene in tobacco plant is Agrobacterium tumefaciens.