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Question #45494
The Question
In an angiosperm species exhibiting gametophytic self-incompatibility, a female plant with the genotype S1S2 is pollinated by a male plant with the genotype S2S3. Following successful pollen-pistil interaction and double fertilization, what proportion of the functional megaspores within the ovules of this female plant will possess the S3 allele?
Options
- A.
50%, because only the S3 pollen successfully germinates and contributes to the ovule.
- B.
25%, due to the independent assortment of alleles during the formation of the embryo sac.
- C.
0%, because megaspores are products of maternal meiosis and are formed prior to fertilization.
- D.
100%, as the S2 pollen is rejected by the pistil, making S3 the sole genetic contributor to the female gametophyte.
Check Your Answer
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
Megasporogenesis|Pollen-Pistil Interaction|Incompatibility Genes
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently conflate the genetic outcome of fertilization (the zygote's genotype) with the structures that precede it.
When presented with a genetic cross, the common trap is to immediately calculate the progeny's genotypes (which would indeed all contain S3 since S2 is rejected) and erroneously apply those ratios to the megaspore, failing to recognize that the megaspore is a strictly maternal, pre-fertilization haploid cell.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Megasporogenesis Symmetry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |