There are three main types of cell division: binary fission, mitosis, and meiosis. Binary fission is how bacteria copy themselves. Mitosis makes identical body cells for growth and repair. Meiosis makes the sex cells (sperm and eggs) with half the usual chromosomes. A fourth process, amitosis, is a minor case that shows up in a few specialized cells.
The names get mixed up constantly, mostly because the stage names overlap. This guide sorts them out, starting with a comparison table you can screenshot for your exam notes.
Contents
- The three types side by side
- Binary fission: how bacteria divide
- Mitosis: copies for growth and repair
- Meiosis: halving the chromosomes
- Amitosis: the odd one out
- Which one happens where
- When cell division goes wrong
- FAQ
The three types side by side
| Binary fission | Mitosis | Meiosis | |
|---|---|---|---|
| Who does it | Bacteria and archaea | Eukaryotic body (somatic) cells | Eukaryotic germ cells |
| Number of divisions | 1 | 1 | 2 |
| Daughter cells | 2 | 2 | 4 |
| Chromosome number | Same as parent | Same as parent (diploid stays diploid) | Half of parent (diploid to haploid) |
| Genetically identical? | Yes (barring mutations) | Yes | No, each cell is unique |
| Purpose | Reproduction | Growth, repair, replacement | Making gametes, shuffling genes |
One detail the table hides: bacteria don’t have a nucleus or a spindle—they are prokaryotic cells—so binary fission is mechanically much simpler than the other two. Eukaryotic division needs a whole apparatus of spindle fibers to sort chromosomes.
Binary fission: how bacteria divide
A bacterial cell has one circular chromosome. Before dividing, it copies that chromosome, and the two copies move toward opposite ends of the cell. The cell then elongates and a ring of protein called FtsZ pinches the middle inward until the cell splits in two.
That’s it. No phases, no spindle.
The speed is the point. Under ideal conditions, E. coli can divide roughly every 20 minutes. One cell becomes two, two become four, and after about seven hours a single bacterium can have produced millions of descendants. This is why a contaminated sample on a lab bench turns cloudy overnight.
Some single-celled eukaryotes, like amoebas, also split in half, and you’ll sometimes see this called binary fission too. In those cases the nucleus divides by mitosis first.
Mitosis: copies for growth and repair
Mitosis produces two daughter cells with exactly the same DNA as the parent. A human skin cell has 46 chromosomes; after mitosis, both new cells have 46 as well.
It’s one stage of a longer loop called the cell cycle. Most of the cycle is interphase, when the cell grows and copies its DNA. Mitosis itself, the actual division, is the short part. Then the cytoplasm splits in a step called cytokinesis.
Remember the four phases with PMAT: Prophase, Metaphase, Anaphase, Telophase.
- Prophase. The copied DNA condenses into visible chromosomes, each made of two identical sister chromatids joined at the centromere. The nuclear envelope breaks down and spindle fibers start forming.
- Metaphase. The chromosomes line up along the middle of the cell, called the metaphase plate. This is the easiest stage to spot under a microscope, because everything sits in a neat row.
- Anaphase. The sister chromatids are pulled apart and dragged to opposite poles. Each chromatid now counts as its own chromosome.
- Telophase. Two new nuclear envelopes form, the chromosomes loosen, and the spindle disappears. Cytokinesis finishes the job, producing two separate cells.
The National Human Genome Research Institute gives a compact definition if you need one to cite.
Mitosis isn’t a free-for-all. The cell checks itself at several points: one before copying DNA (G1), one before entering mitosis (G2), and the spindle assembly checkpoint during metaphase, which blocks anaphase until every chromosome is properly attached to the spindle. These checkpoints are why cells rarely split with missing or extra chromosomes.
Meiosis: halving the chromosomes
Meiosis exists to solve one problem. If sperm and egg each carried 46 chromosomes, the embryo would have 92. So meiosis cuts the number in half, producing haploid cells with 23 chromosomes in humans. Fertilization then restores 46.
It has two rounds of division and one round of DNA copying, which is how one cell ends up as four.
Meiosis I: homologous pairs separate
Meiosis I is where the real action is. Its stages carry the same names as mitosis, with a “I” tacked on.
- Prophase I. Matching chromosomes (one from each parent) pair up tightly. While paired, they swap segments in a process called crossing over. This is the main reason you don’t look identical to your siblings.
- Metaphase I. The pairs line up at the middle, with each pair facing opposite poles. Which side each chromosome lands on is random, which adds another layer of shuffling.
- Anaphase I. The pairs are pulled apart. Unlike mitosis, the sister chromatids stay together here. Whole chromosomes move.
- Telophase I. Two cells form, each now haploid.
Meiosis II: sister chromatids separate
Meiosis II looks like mitosis. No DNA copying happens beforehand. In anaphase II the sister chromatids finally split, and the four resulting cells each hold a single copy of each chromosome.
The difference between the two rounds is the cleanest way to remember it: meiosis I separates pairs, meiosis II separates chromatids. Here’s the meiosis definition from NHGRI if you want the short version.
Between crossing over and random alignment, a single person can produce more than 8 million different chromosome combinations in their gametes, even before counting the swapped segments. That’s the evolutionary payoff of the whole process.
Amitosis: the odd one out
Amitosis is direct division: the nucleus simply pinches in two with no spindle, no condensed chromosomes, no phases. It’s not a standard route for animal or plant cells, and the DNA isn’t distributed evenly.
You’ll find it in the macronucleus of ciliates like Paramecium, and it has been reported in some specialized tissues. Textbooks that list “four types of cell division” are counting this one. Most exams only expect the first three.
Which one happens where
Match the process to the job:
- Healing a cut: mitosis. Skin cells next to the wound divide to fill the gap.
- Growing from a fertilized egg to an adult: mitosis, trillions of times over.
- Replacing cells that wear out: mitosis. Cells lining your gut are replaced every few days.
- Making sperm in the testes or eggs in the ovaries: meiosis.
- A bacterial infection spreading: binary fission.
- Spore formation in many fungi and plants: meiosis, followed by mitosis in the cells that result.
The rule of thumb: if the cells are supposed to match the parent, it’s mitosis or binary fission. If the cells are supposed to be sex cells with a shuffled genome, it’s meiosis.
When cell division goes wrong
The consequences of errors are a big part of why this topic matters, and they’re missing from many textbook summaries.
Errors in meiosis usually come from nondisjunction, where chromosomes fail to separate. The result is a gamete with an extra or missing chromosome. If that gamete is fertilized, the embryo may have an abnormal chromosome count. Down syndrome, for example, is caused by an extra copy of chromosome 21, as explained by the CDC.
Errors in mitosis are different. They happen in body cells, so they aren’t inherited. But if the checkpoints fail and a cell keeps dividing without control, the outcome can be a tumor. The National Cancer Institute describes cancer as exactly this: cells that ignore the signals telling them when to stop dividing.
So the same machinery, in different cells, produces different problems. A meiosis mistake affects the next generation. A mitosis mistake affects the individual.
FAQ
What is the difference between mitosis and meiosis?
Mitosis makes two identical diploid cells in one division. Meiosis makes four genetically different haploid cells in two divisions. Mitosis is for growth and repair, meiosis is for reproduction.
Why does meiosis produce four cells?
Because it has two divisions with only one round of DNA copying. One cell becomes two in meiosis I, and each of those splits again in meiosis II. In human females, three of the four cells in each set are tiny and discarded, so only one becomes a mature egg.
Is binary fission the same as mitosis?
No. Binary fission happens in prokaryotes, which have no nucleus and no spindle. Mitosis needs a nucleus and a spindle, and runs through distinct phases.
How do I remember the phases of mitosis?
PMAT: Prophase, Metaphase, Anaphase, Telophase. Add an “I” at the front (interphase) if your teacher wants the full cycle: IPMAT.
Does mitosis make genetically identical cells?
Almost always. Small copying errors (mutations) can occur, but the process itself is designed to produce exact copies.
Are there more than three types of cell division?
Three are standard: binary fission, mitosis, and meiosis. Amitosis is sometimes listed as a fourth, but it’s rare and not usually tested.
