Question:
Heterosis cannot be fixed, if it is obtained through-
A. Apomixis
B. Balanced lethal system
C. Development of F1 hybrid
D. Development of synthetic variety
E. Vegetative propagation
Choose the correct answer from the options given below:
Heterosis cannot be fixed, if it is obtained through-
A. Apomixis
B. Balanced lethal system
C. Development of F1 hybrid
D. Development of synthetic variety
E. Vegetative propagation
Choose the correct answer from the options given below:
A. Apomixis
B. Balanced lethal system
C. Development of F1 hybrid
D. Development of synthetic variety
E. Vegetative propagation
Choose the correct answer from the options given below:
Show Hint
Fixation = No Segregation.
If you see "Clones," "Apomixis," or "Vegetative," heterosis IS fixed.
In traditional sexual breeding (F\( _1 \), Synthetics), heterosis is lost in subsequent generations.
If you see "Clones," "Apomixis," or "Vegetative," heterosis IS fixed.
In traditional sexual breeding (F\( _1 \), Synthetics), heterosis is lost in subsequent generations.
Updated On: Aug 24, 2026
- C, D and E only
- B, C and D only
- B and D only
- C and D only
Show Solution
Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question:
The "fixation of heterosis" means enabling the hybrid vigor to be maintained through successive generations of seed reproduction without loss due to genetic segregation.
Step 2: Detailed Explanation:
• Methods to Fix Heterosis:
- Apomixis (A): Reproduction via seeds without fertilization. The progeny are clones of the mother plant, thus fixing the F\( _1 \) genotype.
- Vegetative Propagation (E): Clonal propagation (cuttings, grafting) bypasses meiosis and segregation entirely, fixing heterosis perfectly.
- Balanced Lethal System (B): A specialized genetic mechanism (seen in Oenothera) where only the heterozygous individuals survive, thus "fixing" the heterosis in the population.
• Methods where Heterosis is NOT Fixed:
- F1 Hybrid (C): Conventional F\( _1 \) hybrids obtained from crossing inbreds will segregate in the F\( _2 \) generation. Farmers must buy new seeds every year because the heterosis is lost through segregation and recombination.
- Synthetic Variety (D): A synthetic is an open-pollinated population. While it exploits heterosis, the level of vigor is lower than a single cross and it changes/stabilizes over generations; it is not "fixed" in the same way a genotype is fixed in apomixis or cloning.
Final Answer:
Heterosis cannot be fixed in conventional seed-produced F\( _1 \) hybrids and synthetic varieties.
The correct combination is C and D only.
The corresponding option is (D).
The "fixation of heterosis" means enabling the hybrid vigor to be maintained through successive generations of seed reproduction without loss due to genetic segregation.
Step 2: Detailed Explanation:
• Methods to Fix Heterosis:
- Apomixis (A): Reproduction via seeds without fertilization. The progeny are clones of the mother plant, thus fixing the F\( _1 \) genotype.
- Vegetative Propagation (E): Clonal propagation (cuttings, grafting) bypasses meiosis and segregation entirely, fixing heterosis perfectly.
- Balanced Lethal System (B): A specialized genetic mechanism (seen in Oenothera) where only the heterozygous individuals survive, thus "fixing" the heterosis in the population.
• Methods where Heterosis is NOT Fixed:
- F1 Hybrid (C): Conventional F\( _1 \) hybrids obtained from crossing inbreds will segregate in the F\( _2 \) generation. Farmers must buy new seeds every year because the heterosis is lost through segregation and recombination.
- Synthetic Variety (D): A synthetic is an open-pollinated population. While it exploits heterosis, the level of vigor is lower than a single cross and it changes/stabilizes over generations; it is not "fixed" in the same way a genotype is fixed in apomixis or cloning.
Final Answer:
Heterosis cannot be fixed in conventional seed-produced F\( _1 \) hybrids and synthetic varieties.
The correct combination is C and D only.
The corresponding option is (D).
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