---
title: "Plasmids — AP Biology Definition & Exam Guide"
description: "Plasmids are small, extra-chromosomal circular DNA molecules found in prokaryotes and some eukaryotes, central to Unit 6 and to how bacteria share genes like antibiotic resistance."
canonical: "https://fiveable.me/ap-bio/key-terms/plasmids"
type: "key-term"
subject: "AP Biology"
---

# Plasmids — AP Biology Definition & Exam Guide

## Definition

Plasmids are small, circular pieces of DNA that exist independently of the chromosomal DNA in bacteria. They often carry genes that provide a survival advantage to the organism, such as antibiotic resistance.

## Related Study Guides

- [6.1 DNA and RNA Structure ](/ap-bio/unit-6/dna-rna-structure/study-guide/29u5wVp2a9rSDLfLGBlD)

## Review

### Related Terms

- Conjugation: This is a process where genetic material is transferred from one bacterial cell to another through direct contact. It's often how plasmids get shared among bacteria.
- Antibiotic Resistance: This refers to the ability of bacteria to resist the effects of an antibiotic. It often occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs designed to cure or prevent infections.
- Transformation: In biology, transformation is a type of genetic exchange where DNA fragments are taken up by a bacterium from its surrounding environment.