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Biology · 2025 · 5 marks
Biotechnology and its ApplicationsBiotechnological Applications in Agriculture5 marksUnderstandlong answer
CBSE 2025 · Region 4 · Set 1 · Q32
(a) Name and explain the biotechnological strategy wherein the infection by the nematode Meloidegyne incognitia can be prevented using Agrobacterium…
(a)
Name and explain the biotechnological strategy wherein the infection by the nematode Meloidegyne incognitia can be prevented using Agrobacterium vectors in the roots of tobacco plant by RNA interference.
OR
(b)
Explain the amplification of gene of interest using the technique of Polymerase chain reaction (PCR).
Marking-scheme solution
• RNA interference or RNAi
• Steps of RNAi
− Using Agrobacterium vectors nematode-specific genes were introduced into the host plants
− The introduction of DNA was such that it produced both sense and anti-sense RNA in the host cells
− Two RNA’s being complementary to each other form a double stranded RNA (dsRNA)
− This initiated RNAi and thus silenced the specific mRNA of the nematode. (consequently the parasite could not survive in a transgenic host expressing specific interfering RNA)
• Each cycle in PCR has three steps:
Denaturation, Annealing, Extension
− Denaturation: DNA subjected to higher temperature, the two strands of DNA separate due to broken hydrogen bonds between nitrogenous bases
− Annealing: Two sets of primers, which are complementary attach on $\displaystyle 3$’ end of both template strands.
− Extension: the new strand of DNA is formed using thermostable
Taq polymerase enzyme (derived from Thermus aquaticus bacterium), extends the primers and the nucleotides provided in the reaction and the genomic DNA act as the template.
− The process of replication of DNA is repeated $\displaystyle 30$ times the segment of DNA is amplified $\displaystyle 1$ billion times i.e. $\displaystyle 1$ billion copies are made.
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.