---
title: "Mitosis — AP Biology Definition & Exam Guide"
description: "Mitosis is the cell-division process that splits replicated chromosomes into two genetically identical nuclei. Learn how it differs from meiosis and shows up on the AP Bio exam."
canonical: "https://fiveable.me/ap-bio/key-terms/mitosis"
type: "key-term"
subject: "AP Biology"
unit: "Unit 4"
---

# Mitosis — AP Biology Definition & Exam Guide

## Definition

In AP Biology, mitosis is the part of the cell cycle where replicated chromosomes are separated into two new nuclei, producing two genetically identical daughter cells, each with the same chromosome number as the parent cell.

## What It Is

Mitosis is how one cell becomes two identical copies of itself. The cell first copies all its DNA, so each [chromosome](/ap-bio/key-terms/chromosome "fv-autolink") now has two sister chromatids. Then a spindle apparatus pulls those sister chromatids apart and packs them into two separate nuclei. The result: two [daughter cells](/ap-bio/unit-5/meiosis/study-guide/FC0aTuODYikjJuhlBO1Z "fv-autolink") that are genetically identical to the parent, with the same chromosome number.

That's the whole point of mitosis: it makes copies, not variety. This is how your body grows, heals wounds, and replaces dead cells. The phases ([prophase](/ap-bio/unit-4/homeostasis-feedback-loops/study-guide/OgMSpwCrEez0qyWtlCAC "fv-autolink"), metaphase, anaphase, telophase) use the same spindle machinery you'll see in meiosis, which is exactly why the AP exam loves to compare the two. Just remember the big difference: mitosis keeps everything the same, while meiosis cuts the chromosome number in half and shuffles genes around.

## Why It Matters

Mitosis sits inside [Unit 4](/ap-bio/unit-4 "fv-autolink") (Cell Communication and Cell Cycle), where it's the regulated end-product of the cell cycle. Learning objective [AP Bio](/ap-bio "fv-autolink") 5.1.B asks you to describe the similarities and differences between mitosis and meiosis, and EK 5.1.B.1 nails the key contrast: both use a spindle to move chromosomes, but they differ in the number of cells produced and the genetic content of those cells. Mitosis also connects to AP Bio 4.6.A and 4.6.B, because checkpoints control when a cell is allowed to divide, and a breakdown of that control is what causes cancer. The exam treats mitosis less as its own giant topic and more as the baseline you compare everything else against.

## Connections

### Meiosis (Unit 5)

This is the comparison the exam always wants. Mitosis = two identical [diploid](/ap-bio/key-terms/diploid "fv-autolink") cells; meiosis = four genetically different haploid gametes. Same spindle machinery, opposite goals. If you can explain that one sentence, you've got AP Bio 5.1.B covered.

### Regulation of the Cell Cycle (Unit 4)

Mitosis doesn't just happen whenever. Checkpoints (controlled by cyclins and [cyclin-dependent kinases](/ap-bio/key-terms/cyclin-dependent-kinases "fv-autolink")) decide whether the cell is ready to divide. When those brakes fail, cells divide uncontrollably, which is cancer (AP Bio 4.6.B).

### Mutations and Nondisjunction (Unit 6)

Errors during mitosis or meiosis can change phenotype (EK 6.7.B.2). If chromosomes fail to separate properly ([nondisjunction](/ap-bio/key-terms/nondisjunction "fv-autolink")), a daughter cell ends up with the wrong chromosome number, causing aneuploidy and developmental disorders.

### [Genetic Diversity (Unit 5)](/ap-bio/key-terms/genetic-diversity)

Mitosis is the control group for diversity: it makes zero. Compare that to meiosis, where crossing over and independent assortment generate variation (AP Bio 5.2.A). Mitosis shows you what genetic variation looks like when the shuffling mechanisms are switched off.

## On the AP Exam

Mitosis shows up most often as the thing you contrast with meiosis. Expect MCQ stems that hand you a cell with chromosomes at the metaphase plate and ask you to figure out which process is happening based on how the chromosomes are arranged and where the spindle attaches. A classic move: homologous chromosomes paired at the plate with kinetochores pulling toward opposite poles means meiosis I, not mitosis. FRQs lean toward meiosis directly (like the 2026 Short FRQ asking about chromosome movement in Meiosis I), but you score points by knowing why mitosis can't do the job of making gametes. Be ready to state the key difference: mitosis produces two identical cells with the parent's chromosome number, while meiosis produces four genetically distinct haploid cells.

## Mitosis vs Meiosis

Mitosis makes two genetically identical daughter cells with the same chromosome number as the parent (for growth and repair). Meiosis makes four genetically unique haploid cells (gametes) with half the chromosome number. They share the spindle apparatus, but mitosis copies while meiosis halves and shuffles. The trap is assuming mitosis can produce gametes, it can't, because gametes need to be haploid.

## Key Takeaways

- Mitosis separates replicated chromosomes into two new nuclei, producing two genetically identical daughter cells with the same chromosome number as the parent.
- Mitosis and meiosis both use a spindle apparatus to move chromosomes, but they differ in the number of cells produced and the genetic content of those cells (EK 5.1.B.1).
- Checkpoints controlled by cyclins and cyclin-dependent kinases regulate whether a cell proceeds through the cell cycle into mitosis, and losing that control can cause cancer.
- Errors during mitosis, like nondisjunction, can change chromosome number and lead to phenotypic changes such as aneuploidy.
- Mitosis is for growth, repair, and replacement, while meiosis is the process required to make haploid gametes for sexual reproduction.

## FAQs

### What is mitosis in AP Biology?

Mitosis is the part of the cell cycle where replicated chromosomes are separated into two new nuclei, producing two genetically identical daughter cells that each have the same chromosome number as the parent cell. It's how organisms grow, heal, and replace cells.

### Does mitosis create genetic variation?

No. Mitosis produces genetically identical cells, so it creates no variation on its own. Genetic diversity comes from meiosis (through crossing over and independent assortment) and from mutations, which is exactly why the AP exam uses mitosis as the contrast point in AP Bio 5.2.A.

### How is mitosis different from meiosis?

Mitosis makes two identical diploid cells with the parent's chromosome number; meiosis makes four genetically unique haploid cells with half the chromosome number. Both use a spindle, but mitosis copies while meiosis halves and shuffles (EK 5.1.B.1).

### Can mitosis produce gametes?

No. Gametes must be haploid, and mitosis keeps the chromosome number the same as the parent. Only meiosis cuts the chromosome number in half, which is why meiosis (not mitosis) is necessary for sexual reproduction in diploid organisms.

### How does mitosis connect to cancer on the AP exam?

Cell cycle checkpoints decide when a cell is allowed to divide. When those checkpoints fail (AP Bio 4.6.B), cells divide uncontrollably through repeated mitosis, which is what cancer is. This links Unit 4 cell cycle regulation directly to disruptions of the cycle.

## Related Study Guides

- [4.6 Regulation of the Cell Cycle](/ap-bio/unit-4/cell-cycle/study-guide/4ztGMFvp0v4KAzL65pOP)
- [5.1 Meiosis](/ap-bio/unit-5/meiosis/study-guide/FC0aTuODYikjJuhlBO1Z)
- [6.7 Mutations](/ap-bio/unit-6/mutations/study-guide/WIuGA11Yy2RsVq8JpSnt)

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