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Onion cell during prophase
Coiled and visible chromosomes in an onion cell during prophase

What is Mitosis?

Mitosis is the part of the cell cycle that results in two genetically identical cells. This is known as asexual cell division or reproduction. Mitosis can be separated into five key phases: prophase, prometaphase, metaphase, anaphase, and telophase. To remember the difference between mitosis and meiosis, which doesn't produce identical cells, a great trick is to remember that the 'i' and the 't' in mitosis stand for "identical two."

The Cell Cycle and Interphase

Before we dive deeper into mitosis, it's important to understand the cell cycle. The cell cycle encompasses the different phases that a cell goes through during its life. The "normal" phase of the cell cycle is called interphase. During interphase, cells grow, carry out their specific functions, and prepare for cell division. It's during this preparation that the cell makes another copy of its DNA, and signals the start of mitosis.

The Stages of Mitosis

  1. Prophase: After receiving a signal to start reproducing, the cell enters the first stage of mitosis, known as prophase. During prophase, the cell's chromatin, which contains its DNA, condenses into tightly coiled structures called chromosomes. At the same time, the nuclear membrane and the nucleolus, a structure responsible for producing ribosomes, both start to break down and dissolve. This allows easier access to the chromosomes in the next stages of mitosis.
  2. Metaphase: During metaphase, the pairs of chromosomes align themselves at the center of the cell, forming what is called the "metaphase plate." This alignment ensures that, during the next step, the chromosomes will be split up equally between the cells.
  3. Anaphase: During anaphase, all the pairs of chromosomes separate and move towards opposite ends of the cell. This ensures that each daughter cell will each have a complete set of identical chromosomes.
  4. Telophase: Finally, the cell enters telophase. During this phase, the cell forms two new nuclear membranes around each set of chromosomes, and the chromosomes start to uncoil again. Additionally, the cell membrane begins to pinch inward, leading to the formation of two separate daughter cells. This splitting of the cells is called cytokinesis or cell cleavage.

Top Facts About Mitosis for Kids

  • 1. Different species have different numbers of chromosomes.

    For example, humans have 46 chromosomes, dogs have 78, and fruit flies have only 8. These chromosomes carry the genes that determine various traits and characteristics of each species. During mitosis, all of these chromosomes are split up evenly into two identical cells.

  • 2. Mitosis occurs at different rates in different types of cells.

    In humans, for example, skin cells and cells in the lining of the intestines divide quickly because they constantly need to be replaced. On the other hand, nerve cells rarely undergo mitosis and mostly stay in the same state throughout our entire lives.