Short answer
Mitosis normally preserves the number of chromosome sets; meiosis reduces it by half. Mitosis divides one nucleus into two corresponding nuclei. Meiosis uses two successive nuclear divisions after one round of DNA copying, producing haploid nuclei from a diploid starting nucleus. 1 2 3
In humans, mitosis supports growth and cell replacement, while meiosis is part of producing eggs and sperm. The essential contrast is how chromosomes are distributed, not simply “two cells versus four.” 3 4
On this page
At a glance
Scroll to compare all columns →
| Feature | Mitosis | Meiosis |
|---|---|---|
| Nuclear divisions | One. | Two: meiosis I and meiosis II. |
| DNA copying beforehand | One round in the preceding S phase. | One round before meiosis I; none between I and II. |
| Chromosome sets in resulting nuclei | Normally the same as the starting nucleus. | Half as many as the diploid starting nucleus. |
| What separates? | Sister chromatids. | Homologous chromosomes in I; sister chromatids in II. |
| Typical nuclear products | Two. | Four. |
| Genetic outcome | Ordinarily matching chromosome complements, subject to errors. | New combinations through chromosome assortment and usually crossing over. |
| Familiar human role | Growth and replacement of cells. | Egg and sperm production. |
Sources: cell cycle and mitosis 1; meiotic mechanisms 2 3; human context 4.
What each thing is
Mitosis is nuclear division that distributes already-copied chromosomes into two nuclei. Division of the rest of the cell, called cytokinesis, commonly accompanies it but is a distinct process. DNA replication occurs during S phase before mitosis, rather than being a stage of mitosis itself. 1
Meiosis is a sequence of nuclear divisions that reduces chromosome sets. A typical diploid starting cell has two corresponding versions of each chromosome, one originally inherited from each parent. These are homologous chromosomes. After DNA copying, each chromosome consists of two sister chromatids, the copies associated with that chromosome. Homologs and sister chromatids are different relationships. 3
Key differences
The first meiotic division separates partners. Homologous chromosomes pair and then separate into different nuclei during meiosis I. The sister chromatids remain together at this stage. 3
The second separates copies. Meiosis II separates sister chromatids without another intervening round of DNA replication. This resembles the chromosome-separation step in mitosis, but the cells enter meiosis II with the reduced chromosome set produced by meiosis I. 3
Meiosis creates new combinations. Homologous chromosomes can exchange corresponding DNA segments through crossing over. Their independent arrangement during meiosis I also changes which inherited chromosomes end up together. These processes explain why the resulting genomes are not simply identical copies of the starting genome. 3
How to tell them apart
In a diagram, follow the chromosomes rather than counting circles. Paired homologous chromosomes separating while sister chromatids remain joined indicates meiosis I. Separation of sister chromatids could represent mitosis or meiosis II; the preceding steps and chromosome-set context distinguish them. 3
A single still image may not reveal the whole process. Two cells could be products of mitosis or the intermediate result of meiosis I. Likewise, an X-shaped copied chromosome is not automatically evidence of meiosis: copied chromosomes occur before both kinds of division. 1 3
Where they overlap
Both processes organize chromosomes and use related cellular machinery to distribute them. Both follow DNA replication in the ordinary cycles discussed here. Shared stage names, such as prophase and metaphase, reflect related events rather than identical outcomes. 1 3
Both must also be distinguished from the entire cell cycle. Preparation, DNA copying, nuclear division, and physical cell separation are connected events, but naming one event does not name them all. 1
Edge cases
Mitosis does not always mean diploid to diploid. Haploid cells can also undergo mitosis. OpenStax uses plant life cycles to illustrate that mitosis can preserve either a haploid or a diploid chromosome complement. 3
Meiosis is not universally an immediate egg-or-sperm factory. The human example is useful, but plant life cycles also include meiotic spore production and a haploid phase in which mitosis occurs. “Halves chromosome sets” travels across these life cycles more reliably than the human-only shortcut. 3
Nuclear division and cell separation can come apart. Cytokinesis need not follow every mitosis, which is why the underlying definitions specify nuclei. 1
Why the distinction exists
Sexual reproduction joins chromosome contributions. Without a reduction step somewhere in the life cycle, repeatedly combining two full diploid contributions would increase chromosome sets across generations. Meiosis supplies that reduction; mitosis preserves a complement while cells multiply. 2 3
Examples and common misconceptions
A typical human body cell has 46 chromosomes. Ordinary mitotic division distributes a corresponding 46-chromosome complement to each daughter nucleus. Human eggs and sperm normally carry 23; fertilization combines those contributions. These are human examples, not universal chromosome numbers. 4
- “DNA is copied twice during meiosis.” It is copied once before the two divisions. 3
- “Two products prove mitosis.” Meiosis I also produces two intermediate products. 3
- “A copied chromosome makes a cell diploid.” Ploidy counts chromosome sets, not whether each chromosome has sister chromatids. 3
- “Every nuclear division immediately splits the cell.” Cytokinesis is a separate event. 1
Sources
Sources checked October 3, 2026. Standard successful division is described; chromosome errors and specialized reproductive exceptions need their own treatment.
- OpenStax, Biology 2e — 10.2 The Cell Cycle. S phase, mitosis, and cytokinesis.
- National Human Genome Research Institute — Meiosis. Chromosome-set reduction and human reproduction.
- OpenStax, Biology 2e — 11.1 The Process of Meiosis. Homologs, sister chromatids, crossing over, two divisions, and life-cycle scope.
- MedlinePlus Genetics — How do cells divide?. Human 46-to-23 comparison and the roles of mitosis and meiosis.