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Question #46984
The Question
In the Ascomycete fungus Neurospora crassa, a researcher induces a mutation that completely inhibits the activity of the recombinase enzyme during the sexual life cycle. If a cross is performed between two strains differing in two linked genes (AB and ab), which of the following will be the most likely genetic consequence observed in the resulting ascospores?
Options
- A.
The asci will contain 50% recombinant and 50% parental ascospores due to the independent assortment of homologous chromosomes at anaphase I.
- B.
The ascospores will exclusively display parental gene combinations, making the genetic variation for these loci identical to that of asexually produced conidia.
- C.
The ascospores will exhibit a high frequency of non-parental types due to the failure of the synaptonemal complex to stabilize the bivalents.
- D.
The asci will fail to undergo karyogamy, resulting in the formation of dikaryotic ascospores that genetically mimic the parental strains.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Dikaryophase|Basidiomycetes|Meiosis_in_Basidium
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume sexual reproduction inherently guarantees genetic variation.
This question tests the mechanistic understanding that for linked genes, variation is strictly dependent on the enzymatic action of recombinase during pachytene.
It also integrates Class 11 Fungal morphology (conidia vs ascospores) with Class 12 Genetics (Linkage and Recombination).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biological Classification - Class 11 |
| Concept | Fungal Sexual Lifecycle Stages |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |