Select the incorrect statement

Options

A. RNAi silencing takes place in all eukaryotic organisms as a method of celluiar defense
B. RNAi requires silencing of mRNA by binding of complementary ssDNA molecule
C. Complementary nucleic acid could be from mobile genetic elements (transposons)
D. Ti plasmid with nematode specific genes have been used in RNAi

Answer

To solve the question "Select the incorrect statement," we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "RNAi silencing takes place in all eukaryotic organisms as a method of cellular defense."
- This statement is correct. RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, and it is indeed a method of cellular defense found in all eukaryotic organisms.

2. **Statement 2**: "RNAi requires silencing of mRNA by binding of complementary single-stranded DNA molecule."
- This statement is incorrect. RNAi involves the binding of complementary RNA molecules, specifically small interfering RNA (siRNA) or microRNA (miRNA) to mRNA, not single-stranded DNA. The presence of uracil in RNA instead of thymine in DNA makes this binding incompatible.

3. **Statement 3**: "Complementary nucleic acids could be formed from mobile genetic elements called transposons."
- This statement is correct. Transposons, or jumping genes, can move within the genome and can form complementary nucleic acids during their transposition process.

4. **Statement 4**: "TI plasmid or tumor-inducing plasmid with nematode specific gene have been used in RNAi or RNA interference."
- This statement is correct. TI plasmids are used in genetic engineering and can carry genes that are specific to nematodes, and they can be utilized in RNAi applications.

### Conclusion:
After analyzing all the statements, the incorrect statement is **Statement 2**: "RNAi requires silencing of mRNA by binding of complementary single-stranded DNA molecule."

### Final Answer:
The incorrect statement is **Statement 2**.

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