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Question #45847
The Question
A high-yielding hybrid crop with the genotype AaBb is genetically engineered to reproduce obligately via apomixis (specifically, where a diploid megaspore mother cell develops directly into an embryo without reduction division). Which of the following represents the expected genotypic ratio of its seed progeny and the correct biological rationale?
Options
- A.
9:3:3:1 ; Apomixis mimics sexual reproduction, allowing independent assortment during seed formation.
- B.
1:1:1:1 ; The Law of Segregation operates normally, but syngamy is bypassed.
- C.
100% AaBb ; The circumvention of meiosis biologically nullifies both the Law of Segregation and Independent Assortment.
- D.
100% homozygous dominant or recessive ; Apomictic embryos develop from haploid eggs that undergo spontaneous chromosome doubling.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Mendelian Dihybrid Exceptions|Apomixis Genetics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often misinterpret the NCERT line 'apomixis mimics sexual reproduction' to mean it involves meiotic segregation.
The trap relies on failing to connect the absence of meiosis in apomixis (Chapter 2) with the chromosomal basis of Mendelian inheritance (Chapter 5), specifically that bypassing meiosis abolishes segregation, thereby freezing the heterozygous genotype.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Mendelian Dihybrid Exceptions |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |