125. In genetically modified Dhara Mustard Hybrid – 11, male sterility is conferred by ………, while …………..
restores fertility.
(1) barnase, barstar
(2) barstar, barnase
(3) bar, barnase
(4) barnase, bar

Detailed Explanation:

Question:
In genetically modified Dhara Mustard Hybrid – 11, male sterility is conferred by ………, while ………….. restores fertility.

✅ Correct Answer: (1) barnase, barstar

Understanding the Barnase-Barstar System in GM Mustard

The Barnase-Barstar system is a genetic mechanism used to create male sterility and subsequently restore fertility in genetically modified (GM) mustard hybrids like Dhara Mustard Hybrid-11 (DMH-11). This technique is crucial for the production of hybrid seeds.

How It Works:

Barnase – Induces Male Sterility

• Barnase is a ribonuclease enzyme derived from Bacillus amyloliquefaciens.

• It is expressed specifically in the tapetum cells of the anther, where pollen is formed.

• The enzyme destroys the RNA in these cells, causing male sterility by preventing pollen development.

Barstar – Restores Fertility

• Barstar is an inhibitor protein that binds to barnase and neutralizes its activity.

• When barstar is co-expressed in the plant, it restores fertility by protecting the anther cells from barnase’s destructive action.

• This allows successful pollination and seed formation in hybrid crops.

Why This System Is Important:

• Efficient Hybrid Production: Male sterility ensures controlled cross-pollination, which is essential for hybrid vigor (heterosis).

• No Manual Emasculation: It eliminates the need for tedious manual removal of male parts in flowers.

• Precise Control: Genetic control of fertility enables better seed yield and quality in mustard and other crops.

Explanation of Other Options:

• (2) Barstar, barnase – Incorrect order; barstar restores, while barnase induces sterility.

• (3) Bar, barnase – The bar gene confers herbicide resistance, not involved in fertility regulation.

• (4) Barnase, bar – Again, bar is unrelated to the male sterility/fertility mechanism.

Conclusion:

In Dhara Mustard Hybrid-11, the barnase-barstar system offers a powerful tool for genetically engineering hybrid crops. Barnase induces male sterility, preventing self-pollination, while barstar ensures that fertility can be restored in the hybrid generation, facilitating efficient and high-yielding mustard production.

✅ Correct Answer: (1) barnase, barstar