The Question is from neet-zoology reproduction , and it was created by the author K SUNKANNA

Question

In a hypothetical plant species, the endosperm is diploid and the embryo is triploid.  Which of the following most accurately describes the process leading to this unusual ploidy?

K SUNKANNA · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Plant reproduction, specifically double fertilization in angiosperms and ploidy.
 **Related Topics**: Meiosis, mitosis, gamete formation, embryo sac development, endosperm development.
 **Prerequisites**: Understanding of meiosis and mitosis, haploid and diploid chromosome numbers, and the process of double fertilization in flowering plants.
## SOLUTION PATHWAY
**Given Information**:
  Endosperm is diploid (2n).
  Embryo is triploid (3n).
  Standard double fertilization results in a triploid endosperm and a diploid embryo. This question presents an unusual scenario.
**Method & Steps**:
 1. Analyze the ploidy of the resulting endosperm and embryo.
  Reasoning: We need to determine which option results in a 2n endosperm and a 3n embryo.
  Formula/Rule:  Ploidy is determined by the number of chromosome sets.
 2. Examine each option for the ploidy of the gametes and central cell involved in fertilization.
  Working: Let's analyze each option:
  Option A: A diploid megaspore mother cell undergoes mitosis to form a diploid embryo sac (2n). A diploid male gamete (2n) fuses with a haploid central cell (n) resulting in a triploid embryo (3n) and a diploid endosperm (2n)  (2n + n = 3n and 2n + 0 = 2n).
  Option B: A haploid megaspore mother cell undergoes meiosis to form a haploid embryo sac (n). A diploid male gamete (2n) fuses with a diploid central cell (2n) resulting in a tetraploid embryo (4n) and a triploid endosperm (3n) (2n + 2n = 4n and 2n + n = 3n).
  Option C: A triploid megaspore mother cell undergoes mitosis to form a triploid embryo sac (3n). A haploid male gamete (n) fuses with a diploid central cell (2n) resulting in a tetraploid embryo (4n) and a triploid endosperm (3n) (n + 2n = 3n and 3n + 0 = 3n).
  Option D: A diploid megaspore mother cell undergoes meiosis to form a haploid embryo sac (n). Two haploid male gametes (n) fuse with a haploid central cell (n) resulting in a triploid embryo (3n) and a diploid endosperm (2n) (2n + n = 3n and n + n = 2n). This is not correct, as it would require two male gametes fusing with the central cell to get a diploid endosperm, which is not typical.
 3. Select the option that correctly produces the given ploidy.
  Result: Option A correctly leads to a triploid embryo (3n) and a diploid endosperm (2n).
  Verification: The fusion of a diploid male gamete with a haploid central cell yields a triploid embryo.  A diploid megaspore mother cell producing a diploid embryo sac is unusual but possible through mitotic errors, and the fusion of only one male gamete with the central cell produces the diploid endosperm.
 ## OPTION ANALYSIS
A ✓: Correctly explains the formation of a triploid embryo and a diploid endosperm through the fusion of a diploid male gamete with a haploid central cell within a diploid embryo sac.
B :x: Results in a tetraploid embryo, not a triploid one.
C :x: Results in a tetraploid embryo, not a triploid one.
D :x:  Involves two male gametes fusing with the central cell, which is atypical for double fertilization and doesn't produce the stated ploidies.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing mitosis and meiosis:  Understanding the difference in chromosome number after each process is crucial.
  2.Incorrectly applying the principles of double fertilization:  Remember that usually one male gamete fertilizes the egg and the other fertilizes the central cell.
 **Quick Tips**:
  1.Draw a diagram showing the chromosome numbers at each step.
  2.Remember the standard double fertilization process and how it can be modified in unusual scenarios.

K SUNKANNA · Answer

The correct Option is "Diploid megaspore mother cell undergoes mitosis to form the embryo sac, and a diploid male gamete fuses with a haploid central cell."

K SUNKANNA · Answer

Haploid megaspore mother cell undergoes meiosis to form the embryo sac, and a diploid male gamete fuses with a diploid central cell.

K SUNKANNA · Answer

Triploid megaspore mother cell undergoes mitosis to form the embryo sac, and a haploid male gamete fuses with a diploid central cell.

K SUNKANNA · Answer

Diploid megaspore mother cell undergoes meiosis to form the embryo sac, and two haploid male gametes fuse with a haploid central cell.

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