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Step-by-Step Explanation
1. Introduction
Polyploidy is a condition in which a cell or organism has more than two complete sets of chromosomes. In many plant species, this phenomenon is fairly common and can arise due to errors during cell division (mitosis or meiosis). In this question, the plant cell in telophase fails to form a cell plate and ends up with an increased number of chromosomes, indicating polyploidy.
2. Failure in Cell Plate Formation
Normally, in plant cells during telophase, a cell plate forms at the equatorial plane to separate the dividing cell into two daughter cells, each containing an identical set of chromosomes. Failure to form the cell plate causes the cytoplasm not to divide properly, leaving the chromosomes in a single continuous cell. As a result, the cell retains more than the standard number of chromosomes.
3. Definition of Polyploidy
Polyploidy refers to the presence of extra sets of chromosomes in a cell, such that instead of the usual diploid ($2n$) chromosome number, a cell may become triploid ($3n$), tetraploid ($4n$), or even higher. This can occur through:
Non-disjunction during Mitosis: When all chromosomes fail to separate properly, leading to daughter cells with extra sets of chromosomes.
Non-disjunction during Meiosis: Gametes may end up with extra chromosomes, and upon fertilization, produce polyploid offspring.
4. Significance in Plants
Polyploidy is especially significant in the plant kingdom. Polyploid plants often exhibit advantages such as increased size, greater biomass, and sometimes enhanced resistance to environmental stress. This makes polyploidy an important factor in plant evolution and breeding.
5. Conclusion
Given the observation of a cell at telophase with no cell plate formation and extra chromosomes, the correct explanation is that this leads to Polyploidy. This phenomenon is more common in plants, arising from non-disjunction events during cell division, resulting in cells or organisms with more than two complete sets of chromosomes.
