1. Replication of DNA: Before mitosis begins, the DNA within the nucleus replicates itself. This creates two identical copies of the entire genome.
2. Condensation of Chromosomes: The replicated DNA condenses into compact structures called chromosomes. Each chromosome now consists of two identical sister chromatids held together by a centromere.
3. Nuclear Envelope Breakdown: The nuclear envelope, which surrounds the nucleus, breaks down, allowing the chromosomes to be accessed by the mitotic spindle.
4. Chromosome Alignment: The mitotic spindle, a structure made of microtubules, attaches to the centromeres of the chromosomes. This helps align the chromosomes at the center of the cell, forming the metaphase plate.
5. Separation of Sister Chromatids: During anaphase, the spindle fibers pull the sister chromatids apart, separating them to opposite poles of the cell.
6. Nuclear Envelope Reformation: Once the chromosomes reach the poles, the nuclear envelope reforms around each set of chromosomes, creating two separate nuclei.
7. Division of the Cell: Cytokinesis, the division of the cytoplasm, occurs concurrently with the formation of the new nuclei. This results in two daughter cells, each with a complete set of chromosomes enclosed within a nucleus.
In summary, the nucleus in mitosis is responsible for:
* Replicating the DNA
* Condensing the DNA into chromosomes
* Organizing and aligning the chromosomes
* Ensuring that each daughter cell receives a complete copy of the genome
This careful and controlled process of nuclear division ensures that each new cell receives a complete and accurate copy of the genetic information from the parent cell.
