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Question #45594
The Question
In a comparative genetic analysis between flower colour in Antirrhinum majus and the AB blood group in humans, a student observes that both F1 heterozygotes fail to resemble either homozygous parent, and both yield a 1:2:1 phenotypic ratio in the F2 generation. Which of the following statements correctly distinguishes the molecular basis of these two allelic interactions?
Options
- A.
Both phenomena represent a violation of Mendel's Law of Segregation, as the alleles blend in Antirrhinum but remain discrete in the AB blood group.
- B.
The F1 phenotype in Antirrhinum results from a dosage-dependent quantitative reduction of a functional enzyme, whereas the AB blood group phenotype results from the simultaneous, independent expression of distinct antigenic glycoproteins.
- C.
In Antirrhinum, the recessive allele produces a modified, hyperactive enzyme, whereas in the AB blood group, both alleles produce non-functional gene products.
- D.
Both interactions demonstrate identical phenotypic and genotypic ratios (1:2:1) because the alleles physically interact and alter each other's DNA sequence during gametogenesis.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Mirabilis jalapa|ABO Blood Grouping|Allelic variation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the molecular mechanisms of Incomplete Dominance and Co-dominance because both result in a 1:2:1 F2 ratio and an F1 that doesn't match either parent.
The trap lies in distinguishing between a 'quantitative dosage effect' (blended phenotype due to half the enzyme) and 'qualitative independent expression' (both distinct proteins are fully expressed).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Incomplete Dominance Pheno-Geno |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |