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Question #45320

Difficulty: 8/10 | 🟢 Free

The Question

A plant breeder develops a highly desirable heterozygous hybrid angiosperm ( $2n=40$ ) with genotype $AaBb$ . To prevent the loss of hybrid vigor in subsequent generations, the breeder selects a mutant line that exclusively reproduces via apomixis (specifically, the development of an unreduced egg cell into an embryo without fertilization). Which of the following accurately describes the genetic and stoichiometric outcome of this apomictic process compared to normal amphimixis?

Options

A.
The apomictic embryo bypasses the standard 1:1 (male gamete:egg) syngamy stoichiometry, developing directly into a $2n=40$ ( $AaBb$ ) clone, thereby completely nullifying Mendelian segregation.
B.
Since syngamy is bypassed, the apomictic embryo develops from the fusion of a male gamete with a diploid secondary nucleus, resulting in a triploid ( $3n=60$ ) clone.
C.
The unreduced egg cell ( $2n=40$ ) develops without syngamy, but undergoes independent assortment during its first mitotic cleavage, resulting in a loss of hybrid vigor.
D.
The apomictic process bypasses syngamy, but still requires normal meiosis to form the egg cell, which then undergoes endoreduplication to form a $2n=40$ homozygous embryo.

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

Synergids|Polar_Nuclei|Embryo_Sac|Apomixis_Genetics

Why This Question Is Tricky

Common Mistakes

Conceptual Pivot: Students often fail to connect the cytological mechanism of apomixis (absence of meiosis and syngamy) with its ultimate genetic consequence (cessation of Mendelian segregation).

The trap lies in assuming that because a seed is formed, some form of segregation, fertilization stoichiometry, or meiotic recombination must have occurred.

Option A correctly synthesizes the bypass of fertilization stoichiometry with the genetic outcome of cloning.

Quick Facts About This Question

Question Information

Subject	Biology
Chapter	Sexual Reproduction in Flowering Plants - Class 12
Concept	Double Fertilization Stoichiometry
Difficulty	8
Cognitive Load	5
Target Solve Time	120 sec
Access	Free