Mitosis

One tiny cell can turn into two.

This is how your body grows. First, the cell makes a copy of its instructions. These instructions are in things called chromosomes.

Next, the cell pulls these copies apart. Small threads act like ropes to move them. One set goes to each side. Then, the cell splits in half. Now you have two new cells. They are exactly like the first one.

This helps you stay healthy and strong.

How does one cell become two? This happens through a way called mitosis.

Mitosis is a part of the cell cycle. It makes two new cells that are exactly the same.

Before mitosis starts, the cell must get ready. This is called interphase. During this time, the cell grows. It also makes a copy of its DNA. DNA is the set of instructions for the cell. These instructions are packed into things called chromosomes.

When mitosis begins, the chromosomes become thick and easy to see. In animal cells, the shell around the nucleus breaks down. Tiny threads called microtubules grow from both sides of the cell. These threads attach to the chromosomes. They act like ropes to pull the copies apart.

One set of chromosomes goes to each side.

Next, new shells form around the two sets of DNA. Finally, the cell must split its main body. This part is called cytokinesis. In animal cells, the membrane pinches in the middle. In plant cells, a new wall forms between the two parts.

Now, you have two identical daughter cells.

Have you ever wondered how your body grows or how it fixes itself? It all starts with a tiny process called mitosis.

Mitosis is a special part of the cell cycle. It is how one cell divides to make two new daughter cells. These new cells are genetically identical to the original parent cell. This means they have the exact same instructions inside them. This process is vital because it keeps life stable as cells divide.

Before mitosis can happen, the cell must prepare through a stage called interphase. During the S phase of interphase, the cell makes a copy of its DNA. This DNA is organized into structures called chromosomes.

Once ready, mitosis begins with prophase. The chromosomes condense and become thick and visible. In animal cells, the nuclear envelope breaks down. Then, in prometaphase, tiny fibers called microtubules attach to the chromosomes. These fibers pull the chromosome copies to opposite sides of the cell.

People have studied cell division for a very long time. In 1835, a German botanist named Hugo von Mohl described how cells divide in green algae. Later, in 1875, a Polish scientist named Wacław Mayzel described mitosis in animal cells. He saw it happening in the cells of frogs, rabbits, and cats.

In 1882, Walther Flemming gave the process its name, mitosis. The name comes from a Greek word meaning "warp thread." This name describes how the chromosomes look as they pull apart.

There are many specific details to learn about this process. During metaphase, the chromosomes line up in the middle of the cell. In anaphase, the sister chromatids are pulled apart to opposite ends.

After this, telophase occurs as new nuclei form. Finally, cytokinesis divides the rest of the cell. In animal cells, the membrane pinches inward to split the cell. In plant cells, a new cell plate forms in the middle.

If errors happen, it can lead to problems like cancer or non-viable embryos.

Mitosis works differently depending on the type of living thing. For example, most animal cells undergo an "open" mitosis where the nucleus breaks down. However, fungal cells often have a "closed" mitosis where the nucleus stays intact.

Bacteria and archaea do not use mitosis at all. Instead, they use a different way to divide called binary fission. Most human cells are made through mitosis, but there are exceptions. Your sperm and egg cells are made through a different process called meiosis.

Mitosis is a fundamental process within the eukaryotic cell cycle. It is the mechanism by which a single parent cell divides to produce two genetically identical daughter cells. This process is known as equational division because it maintains the exact same number of chromosomes in each new cell. By ensuring genetic stability, mitosis allows organisms to grow, repair tissues, and replace worn-out cells. Without this precise duplication and separation, life could not maintain the complex instructions required for biological function.

Before mitosis begins, the cell must undergo a long preparation period called interphase. Interphase is divided into three distinct subphases: G1 (first gap), S (synthesis), and G2 (second gap). During the S phase, the cell performs DNA replication, creating an exact copy of its entire genome. These copies consist of two identical sister chromatids held together at a point called the centromere. The cell also grows by producing proteins and various organelles during these stages. Highly regulated proteins, such as cyclins and cyclin-dependent kinases, act as checkpoints to ensure the DNA is undamaged before the cell proceeds to the M phase.

The mitotic phase, or M phase, follows a strict sequence of stages to ensure accuracy. In prophase, the loosely packed chromatin condenses into thick, visible chromosomes. The nucleolus disappears, and gene transcription stops. In animal cells, the centrosomes move to opposite sides of the cell to organize microtubules into a spindle apparatus. In the subsequent stage, prometaphase, the nuclear envelope disintegrates into small vesicles. This allows the microtubules to reach the chromosomes and attach to their centromeres.

As the process continues, the cell enters metaphase and anaphase to organize the genetic material. During metaphase, the spindle fibers pull the chromosomes until they align perfectly in the center of the cell. This alignment is crucial for the next step. In anaphase, the connection between sister chromatids is broken, and they are pulled toward opposite poles of the cell. These separated chromatids are now referred to as daughter chromosomes. As the cell elongates, these chromosomes reach their maximum condensation at the end of this stage.

The final stages of nuclear and cellular division are telophase and cytokinesis. During telophase, a new nuclear envelope forms around each of the two sets of daughter chromosomes. The chromosomes also begin to decondense, returning to their looser chromatin state. Following this, cytokinesis divides the remaining cytoplasm, organelles, and cell membrane. In animal cells, the cell membrane pinches inward to split the cell into two. In contrast, plant cells must construct a new cell plate to divide the cell.

Scientists have spent centuries uncovering the mechanics of cell division. In 1835, the German botanist Hugo von Mohl described cell multiplication in the green algae *Cladophora glomerata*. Later, in 1875, Wacław Mayzel provided the first descriptions of mitosis in animal cells, specifically observing frog, rabbit, and cat cornea cells. The specific term "mitosis" was coined by Walther Flemming in 1882, derived from the Greek word *mitos*, meaning "warp thread." This name reflects the thread-like appearance of the chromosomes during the process.

While mitosis is highly efficient, errors can occur during the process. If a cell undergoes tripolar or multipolar mitosis, it may produce three or more daughter cells instead of two. Such errors can lead to non-viable embryos that fail to implant. Other mistakes can trigger mitotic catastrophe, apoptosis (programmed cell death), or genetic mutations. These mutations are a known cause of certain types of cancers. Furthermore, mitosis varies by organism; for example, fungal cells often undergo "closed mitosis," where the nucleus remains intact, unlike the "open mitosis" seen in most animal cells.