Your body is made up of trillions of cells—tiny building blocks that work together to keep you alive and healthy. Each cell has a specific job, like carrying oxygen, sending messages, or protecting you from illness. Inside every cell is a control center called the nucleus, which contains DNA, the instructions for how the cell functions. To grow, heal, and replace old cells, your body needs a way to make new ones. That’s where mitosis comes in.
Before you learn about mitosis, it’s important to understand chromosomes. Chromosomes are long, threadlike structures made of DNA and proteins. DNA carries all the genetic instructions that tell a cell how to work and what type of cell it will become. Humans have 46 chromosomes in most of their cells, arranged in 23 pairs. These chromosomes must be carefully copied and divided during mitosis so that each new cell gets a complete set of instructions.
Mitosis is the process cells use to make exact copies of themselves. It’s how your body grows, heals injuries, and replaces damaged or worn-out cells. Every time you grow taller, recover from a scrape, or your fingernails get longer, mitosis is taking place.
Before a cell begins mitosis, it goes through a phase called interphase. Interphase is the longest part of the cell cycle, and it’s when the cell gets ready to divide. During this time, the cell grows, carries out its regular functions, and most importantly, copies its DNA. DNA contains the instructions for everything the cell needs to do, so it must be duplicated so that each new cell gets a full set of instructions. The two identical copies of each chromosome are called sister chromatids, and they are connected at a point called the centromere. Although the DNA is copied during interphase, it is still loose and stringy in the nucleus and hasn’t coiled up into the visible chromosome shapes yet. This coiling happens at the very start of mitosis. Interphase is an important step because without it, the cell wouldn’t have the materials or the genetic information needed to divide properly.
Mitosis happens in several steps:
Prophase – The DNA in the nucleus coils into chromosomes, and the nuclear membrane begins to break down.
Metaphase – The chromosomes line up in the middle of the cell.
Anaphase – The chromosomes are pulled apart to opposite ends of the cell.
Telophase – New nuclear membranes form around each set of chromosomes.
Cytokinesis – The cell splits into two new, identical cells.
Each new cell has the same DNAÂ as the original. This is important because it allows the new cells to perform the same tasks, whether they become part of your skin, bones, muscles, or other tissues.
Mitosis is closely related to cell function. Cells must divide to keep your body growing and healthy. Without mitosis, dead or damaged cells couldn’t be replaced, and your body couldn’t repair itself. It also ensures that each new cell has a full set of instructions to do its job correctly.
Mitosis is a form of asexual reproduction. Some simple organisms, like amoebas and bacteria, use mitosis to reproduce by making exact copies of themselves. In humans and other multicellular organisms, mitosis is vital for development and maintenance throughout life.
Even though it’s happening at a microscopic level, mitosis is one of the most important processes in your body, helping you grow, heal, and stay alive every day.
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Middle School Science
