1. DNA Replication:
* Before mitosis even starts: The cell's DNA, housed in chromosomes, undergoes replication. This process creates an exact copy of each chromosome.
* Result: Now, instead of one copy of each chromosome, you have two identical copies linked together called sister chromatids.
2. Mitosis Phases:
* Prophase: The duplicated chromosomes condense and become visible. The nuclear envelope breaks down.
* Metaphase: The chromosomes line up at the center of the cell, forming the metaphase plate. Spindle fibers (made of microtubules) attach to the centromere of each chromosome.
* Anaphase: The sister chromatids are pulled apart by the spindle fibers, moving towards opposite poles of the cell.
* Telophase: The chromosomes reach the poles of the cell, and new nuclear envelopes form around them. The cytoplasm divides (cytokinesis) to create two separate daughter cells.
Why this creates identical DNA:
* Replication: The initial DNA duplication is the key. Each new cell receives a complete set of chromosomes, ensuring the same genetic information.
* Equal Distribution: Mitosis ensures that the duplicated chromosomes are evenly distributed to each daughter cell. The spindle fibers pull the sister chromatids apart, ensuring that one copy of each chromosome goes to each new cell.
In essence, mitosis is a precise division process that ensures that the original cell's genetic information is faithfully replicated and passed on to two genetically identical daughter cells.
