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Question #45268
The Question
In a genetic study of Drosophila, two genes are located 35 map units apart on the same autosome. A researcher introduces a highly specific chemical inhibitor that completely degrades the synaptonemal complex proteins during early Prophase I in the F1 heterozygous females. If these F1 females are subsequently test-crossed, what will be the expected phenotypic ratio of the progeny, and what is the underlying genetic principle?
Options
- A.
65% Parental and 35% Recombinant types, because the physical distance between the genes inherently dictates the recombination frequency.
- B.
1:1:1:1 ratio, because the absence of the synaptonemal complex causes the homologous chromosomes to assort independently.
- C.
1:1 ratio of only Parental types, because the lack of synapsis prevents chiasmata formation, resulting in complete linkage.
- D.
9:3:3:1 ratio, because the disruption of Prophase I forces the cell to bypass recombination and undergo standard independent assortment.
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
Synaptonemal Complex|Linkage Group Calculation|Crossing Over
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often mechanically equate 'Map Distance' with 'Recombination Frequency' (Option A trap) without recognizing that this mathematical relationship is entirely dependent on the physiological assembly of the synaptonemal complex.
The question tests the synthesis of Cell Division (Meiosis) with Genetics (Linkage).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell Cycle and Cell Division - Class 11 |
| Concept | Synaptonemal Complex Assembly |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |