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Question #45845
The Question
In Pisum sativum, the gene responsible for flower colour also controls seed coat colour and red spots in leaf axils. A researcher crosses two plants heterozygous for this gene. The progeny are grown in a specific soil pH that completely inhibits the biochemical pathway for seed coat pigmentation without affecting the other traits. Which of the following is CORRECT regarding the expected phenotypic outcome and the genetic phenomenon involved?
Options
- A.
The progeny will exhibit a 9:3:3:1 ratio for flower and seed coat colour, as environmental stress induces independent assortment of linked traits.
- B.
The progeny will exhibit a 3:1 ratio for flower colour, but all plants will have colourless seed coats, illustrating environmental masking of a pleiotropic gene.
- C.
The progeny will exhibit a 1:2:1 ratio for both traits, indicating that the environmental stress has induced incomplete dominance.
- D.
The progeny will exhibit a 3:1 ratio for both traits, as pleiotropic gene expression is strictly genetically determined and environmentally independent.
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
Mendelian Dihybrid Exceptions|Pleiotropy Logic
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The 'Two Traits = Two Genes' fallacy.
Students reflexively associate any problem mentioning two traits with a dihybrid cross and a 9:3:3:1 ratio.
Furthermore, this question tests the advanced understanding that pleiotropic manifestations can be uncoupled by specific environmental factors (Gene-Environment Interaction), masking the expected 3:1 pleiotropic ratio.
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 |