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Question #45814
The Question
In a wild-type Drosophila, genes P, Q, and R are mapped on Chromosome II. The recombination frequency (RF) between P and Q is 8%, and between Q and R is 12%. A radiation-induced reciprocal translocation breaks Chromosome II exactly between loci Q and R, exchanging the R-bearing segment with a segment from Chromosome III. Based on the Chromosomal Theory of Inheritance, which of the following is the most likely consequence in the mutant flies?
Options
- A.
Genes P and R will continue to show a recombination frequency of approximately 20% because their original nucleotide distance is conserved.
- B.
Genes Q and R will now assort independently, exhibiting an effective recombination frequency of 50%.
- C.
The total number of linkage groups in the organism will decrease by one due to the exchange of chromosomal segments.
- D.
Genes P and Q will lose their linkage and show a recombination frequency of 50% due to the disruption of chromosomal synteny.
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
Chromosomal Theory of Inheritance|Recombination Frequency (RF)|Linkage Group Calculation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'recombination frequency is directly proportional to physical distance' (Sturtevant's logic) without realizing this strictly requires genes to remain on the same homologous pair.
The trap assumes students will think physical distance dictates RF even after a translocation.
The core realization is that structural chromosomal aberrations redefine linkage groups, instantly converting previously linked genes into independently assorting ones (RF = 50%).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Chromosomal Theory of Inheritance |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |