---
title: "Zygote — AP Bio Definition & Exam Guide"
description: "A zygote is the single diploid cell formed when sperm and egg fuse during fertilization. Learn how it ties meiosis, ploidy, and genetic variation together for AP Bio."
canonical: "https://fiveable.me/ap-bio/key-terms/zygote"
type: "key-term"
subject: "AP Biology"
---

# Zygote — AP Bio Definition & Exam Guide

## Definition

A zygote is a fertilized egg formed when two gametes (sperm and egg) fuse together during fertilization. It contains the full set of chromosomes necessary for development into a new organism.

## Review

### Related Terms

- Embryo: An embryo refers to the early stage of development after fertilization when significant cell divisions occur.
- [Mitosis](/ap-bio/key-terms/mitosis): Mitosis is the process by which cells divide and produce genetically identical daughter cells. It plays an important role in the growth and development of an organism.
- Blastocyst: A blastocyst is an advanced stage of embryo development where it forms a hollow ball-like structure with differentiating cell layers.