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: Core Idea:
The question concerns the genetic engineering technique used to slow tomato ripening, with the Flavr Savr tomato as a key example.
Step 2: Elaboration:
Tomato ripening, particularly softening, is largely driven by the enzyme polygalacturonase (PG), which degrades cell wall pectin.
To slow this process, scientists targeted the PG enzyme. They utilized antisense RNA technology to reduce PG enzyme production.
An artificial, reverse-complement (antisense) copy of the PG gene was created.
When transcribed, this gene produces an antisense mRNA molecule.
This antisense mRNA then binds to the normal (sense) PG mRNA, creating double-stranded RNA.
The cell either degrades this double-stranded RNA rapidly or blocks its translation.
This significantly lowers the functional PG enzyme amount. Because this method reduces or eliminates an existing gene's function, it is conceptually a Gene Subtraction Method (also known as gene silencing or knockdown).
The other options are incorrect:
Gene Addition Method involves adding a new gene for a new trait.
Glyphosate resistance relates to herbicide tolerance, not ripening.
Proteinase inhibitors are generally engineered for pest resistance.
Step 3: Conclusion:
The method used to delay ripening by silencing the polygalacturonase gene is a form of gene subtraction.