Question

Ripening delayed tomatoes are produced by

• A. Gene Subtraction Method
• B. Gene Addition Method
• C. Glyphosate resistant crops
• D. Proteinase inhibitors

Hint:

Associate "delayed ripening tomatoes" (like the Flavr Savr) with antisense technology. Antisense technology is a method to silence a gene, which is effectively "subtracting" its function from the organism.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The question asks about the genetic engineering technique used to delay ripening in tomatoes. The most famous example of this is the Flavr Savr tomato.
Step 2: Detailed Explanation:
Fruit ripening, particularly softening, in tomatoes is largely caused by an enzyme called polygalacturonase (PG). This enzyme breaks down pectin in the cell walls.
To delay this process, scientists used a technique to reduce the production of the PG enzyme. This was achieved using antisense RNA technology.
An artificial gene was created that is a reverse-complement (antisense) copy of the natural PG gene.
When this antisense gene is transcribed, it produces an antisense mRNA molecule.
This antisense mRNA binds to the normal (sense) PG mRNA, forming a double-stranded RNA molecule.
This double-stranded RNA is rapidly degraded by the cell, or its translation is blocked.
The result is a significant reduction in the amount of functional PG enzyme produced. Since this method works by reducing or eliminating the function of an existing gene, it is conceptually a Gene Subtraction Method (or gene silencing/knockdown).
The other options are incorrect:
Gene Addition Method would involve adding a new gene to introduce a new trait.
Glyphosate resistance is a trait for herbicide tolerance, unrelated to ripening.
Proteinase inhibitors are typically engineered for pest resistance.
Step 3: Final Answer:
The method used to delay ripening by silencing the polygalacturonase gene is a form of gene subtraction.