Which of the following does NOT occur during mitosis? a.centromeres split b.chromosomes replicate c.spindles form
The Correct Answer and Explanation is :
The correct answer is b. chromosomes replicate.
Explanation
Mitosis is the process of cell division that results in two genetically identical daughter cells, and it consists of several distinct phases: prophase, metaphase, anaphase, and telophase. Each of these phases plays a crucial role in ensuring that the genetic material is accurately divided between the two daughter cells.
- Chromosomes Replicate: The statement that chromosomes replicate (option b) does not occur during mitosis. Instead, chromosome replication occurs during the S phase (synthesis phase) of interphase, which precedes mitosis. During interphase, the DNA in the cell’s nucleus is replicated, resulting in two sister chromatids for each chromosome. These sister chromatids are joined together at a region called the centromere and are prepared for separation during mitosis.
- Centromeres Split: During mitosis, particularly in anaphase, the centromeres do split. This splitting allows the sister chromatids to separate and move toward opposite poles of the cell. Once the centromeres divide, each sister chromatid is pulled apart by the spindle fibers, ensuring that each new daughter cell receives an identical set of chromosomes.
- Spindles Form: The formation of spindle fibers is a critical step that occurs during mitosis, specifically during prophase. The spindle apparatus, which is composed of microtubules, helps organize the chromosomes and facilitates their movement. The spindle fibers attach to the centromeres of the chromosomes and play a key role in aligning them at the metaphase plate and subsequently pulling them apart during anaphase.
In summary, chromosome replication occurs before mitosis during interphase, while the splitting of centromeres and the formation of spindle fibers are integral parts of the mitotic process. Thus, the correct answer is that chromosomes do not replicate during mitosis.