Question

Which of the following method is NOT an example of gene inactivation?

• A. RNAi
• B. Genome editing
• C. T-DNA tagging
• D. Expression under strong promoter

Hint:

Inactivation = Silence/Break/Stop.
RNAi = Silent.
Genome editing = Broken.
T-DNA Tagging = Interrupted.
Strong Promoter = Loud/High Volume (Active!).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify a genetic engineering technique that is intended to increase or maintain gene function, rather than stopping or "inactivating" it.

Step 2: Detailed Explanation:

• RNAi (A): RNA interference is a mechanism of post-transcriptional gene silencing (PTGS). It uses double-stranded RNA to trigger the degradation of specific mRNA transcripts, effectively inactivating the expression of the gene.

• Genome Editing (B): Techniques like CRISPR/Cas9 or TALENs are used to create targeted mutations (indels). This frequently results in "knockouts" where the gene sequence is disrupted, causing permanent inactivation.

• T-DNA Tagging (C): This is a form of insertional mutagenesis. A T-DNA sequence from Agrobacterium is randomly inserted into the genome. If it lands within a gene, it physically disrupts the coding sequence, leading to gene inactivation.

• Expression under strong promoter (D): Placing a gene's coding sequence under a constitutive or "strong" promoter (like the CaMV 35S promoter) is a technique for overexpression. The goal is to produce more of the gene product than the plant normally would. This is the opposite of inactivation.

Step 3: Final Answer:
Expression under a strong promoter is used for gain-of-function or overexpression studies, whereas the other options are classic "loss-of-function" or inactivation strategies.