Which of the following events does not occur during prophase of mitosis?
ANSWVER
Nucleoli disappear.
The centrosomes move away from each other.
The chromosomes condense.
The mitotic spindle forms.
Each duplicated chromosome appears as two identical sister chromatids.
The mitotic spindle breaks down.
The correct answer and explanation is :
The correct answer is “The mitotic spindle breaks down.”
Explanation:
Mitosis is the process by which a eukaryotic cell divides to produce two genetically identical daughter cells. It occurs in several stages, with each stage playing a specific role in ensuring the accurate segregation of the genetic material. The stages of mitosis are prophase, metaphase, anaphase, and telophase.
Prophase:
Prophase is the first stage of mitosis, and several critical events take place:
- Nucleoli disappear: As the cell prepares for division, the nucleolus, which is responsible for producing ribosomal RNA (rRNA), begins to break down. This is essential because the cell focuses on dividing its genetic material and no longer needs the machinery for protein synthesis that the nucleolus provides.
- The centrosomes move away from each other: The centrosomes, which are the microtubule-organizing centers of the cell, begin to move to opposite poles of the cell. This movement helps in the formation of the mitotic spindle, which is crucial for chromosome separation later in mitosis.
- The chromosomes condense: During prophase, the chromatin (a complex of DNA and proteins) condenses into distinct, visible chromosomes. This condensation is essential because it makes the chromosomes more manageable for the division process, and they can be easily moved around during mitosis.
- The mitotic spindle forms: The mitotic spindle, which is composed of microtubules, begins to form. The microtubules extend from the centrosomes and begin to capture and organize the chromosomes. The spindle fibers will later attach to the centromeres of the chromosomes, ensuring that each sister chromatid is pulled to opposite sides of the cell.
- Each duplicated chromosome appears as two identical sister chromatids: During prophase, the chromosomes have already been replicated during the S-phase of the cell cycle. As a result, each chromosome consists of two identical sister chromatids connected at the centromere. These sister chromatids will later be separated into the two daughter cells.
What does not happen in prophase?
- The mitotic spindle breaks down: This does not happen during prophase. Instead, the mitotic spindle forms during prophase, and it plays a critical role in organizing and segregating the chromosomes. The spindle breaks down later, during telophase, as the process of mitosis concludes and the cell begins to reassemble its structures for cytokinesis.
In summary, the mitotic spindle breaking down is not an event that occurs in prophase. It occurs in telophase, the final stage of mitosis.