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One cell becomes two. How does each new cell end up with a full set of chromosomes?
Cell Division lab · Last updated: 16 October 2026
One cell becomes two, again and again, as you grow and heal. In this 3D lab, you follow chromosomes as they are copied, lined up and pulled apart so that each new cell ends up with a complete set. It shows why a cut can heal and how a single cell grows into a whole body.
What you'll discover
- A cell copies all its chromosomes before it divides, so there are two identical copies of each.
- The copies line up in the middle and are pulled to opposite ends, one copy to each side.
- Ordinary body cells divide by mitosis, while sex cells form by meiosis, which halves the number of chromosomes.
The science in plain words
Your body grows and repairs itself by making new cells, and every new cell comes from an existing one dividing in two. The challenge is making sure each daughter cell gets a complete set of genetic instructions. Human body cells carry 46 chromosomes, long strands of DNA that hold those instructions.
Before dividing, the cell copies all of its DNA. Each chromosome then exists as two identical sister chromatids joined at a pinch point. During mitosis the chromosomes coil up tightly so they are easier to move, line up across the middle of the cell, and are pulled apart by spindle fibres so that one copy of each heads to opposite ends. A new nucleus forms around each set, and the cell pinches in two. The result is two cells with identical chromosomes.
A second kind of division, meiosis, makes sperm and egg cells. It splits twice and halves the chromosome number to 23, so that when a sperm and an egg join, the new cell is back to 46. Meiosis also shuffles genes, which is one reason brothers and sisters look different. When control of division breaks down, cells can multiply unchecked, which is what happens in cancer.
Where it fits
Common questions
What is the difference between mitosis and meiosis?
Mitosis makes two identical cells with the full number of chromosomes and is used for growth and repair. Meiosis makes four sex cells, each with half the chromosomes and a different mix of genes. Mitosis keeps things the same, while meiosis creates variety.
How many chromosomes do humans have?
Most human cells have 46 chromosomes, arranged in 23 pairs. One chromosome of each pair comes from the mother and one from the father. Sperm and egg cells carry just 23 chromosomes, so a fertilised egg ends up with the full 46.
Why do cells need to divide?
Cells divide so that living things can grow, replace worn-out cells and repair injuries such as cuts and broken bones. Single-celled organisms like bacteria and amoeba also divide to reproduce. Each division has to pass on a full copy of the DNA so the new cells work properly.
Related labs
- DNA Replication: Before a cell divides it copies all its DNA. How does it copy it so well?
- Genetic Inheritance: Two purple-flowered plants can have white-flowered babies. How?
- Protein Folding: A protein is a long chain. How does it fold itself into exactly the right shape?
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Try it yourself
The Cell Division lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.