Direct comparison
Plasmid vs Chromosome: Key Differences in Bacteria
Plasmid vs chromosome compared: location, shape, copy number, independent replication and bench use, each row cited to NHGRI, Addgene and OpenStax.
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How do Plasmid, Chromosome compare side by side?
The table below compares Plasmid, Chromosome across 9 procurement-relevant dimensions, from what it is through source.
Side-by-side comparison
| Dimension | Plasmid | Chromosome |
|---|---|---|
| What it is | A small circular DNA molecule found in bacteria and some other microscopic organisms (NHGRI). Small, circular, double-stranded (OpenStax). | The cell's main DNA molecule. Bacteria generally have a single, circular chromosome (OpenStax). |
| Where it sits in the cell | Extrachromosomal DNA: DNA that is not part of the chromosome (OpenStax). Physically separate from chromosomal DNA (NHGRI). | Located in a nucleoid, not bound by a complex nuclear membrane (OpenStax). |
| Shape and ploidy | Small, circular, double-stranded DNA molecules (OpenStax). | Typically circular and haploid (unpaired) in prokaryotes (OpenStax). |
| Number per cell | Cells that have plasmids often have hundreds of them within a single cell (OpenStax). Copy number is controlled by the origin of replication (Addgene). | Bacteria generally have a single chromosome (OpenStax). |
| How it replicates | Replicates independently of the chromosome (NHGRI, Addgene). All natural plasmids contain an origin of replication, which controls host range and copy number (Addgene). | The host chromosome that plasmids replicate independently from (Addgene). |
| Role in the cell | Often carry genes that confer advantageous traits such as antibiotic resistance, and are important to the survival of the organism (OpenStax). Can be passed from one cell to another (NHGRI). | Holds the cell's main genome, the molecule plasmids replicate independently of (Addgene, NHGRI). |
| Use at the bench | Scientists splice genes they want to study into a plasmid using recombinant DNA methods; when the plasmid copies itself, it also copies the inserted gene (NHGRI). | The host chromosome that the plasmid, with its inserted gene, replicates independently of (Addgene, NHGRI). |
| Pick which when | Treat the plasmid as the unit you engineer, carry a gene on, and copy: you are inserting a gene and want it replicated with the plasmid. | Treat the chromosome as the host genome: you are describing the cell's own DNA or what the plasmid replicates independently of. |
| Source | NHGRI Genetics Glossary, "Plasmid" (genome.gov/genetics-glossary/Plasmid); Addgene blog, "Plasmids 101: What is a plasmid?" (blog.addgene.org/plasmids-101-what-is-a-plasmid). Read 2026-10-29. | OpenStax Microbiology, "Unique Characteristics of Prokaryotic Cells" (openstax.org/books/microbiology/pages/3-3-unique-characteristics-of-prokaryotic-cells). Read 2026-10-29. |
Common questions
Common questions about Plasmid vs Chromosome
Is a plasmid a chromosome?
+
No. OpenStax describes plasmids as extrachromosomal DNA, DNA that is not part of the chromosome, and NHGRI states that plasmids are physically separate from chromosomal DNA. Bacteria generally have a single, circular chromosome in a nucleoid, while a plasmid is a separate small, circular, double-stranded molecule.
Do plasmids replicate independently of the chromosome?
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Yes. NHGRI states that plasmids replicate independently, and Addgene describes plasmids as small circular pieces of DNA that replicate independently from the host's chromosomal DNA. All natural plasmids contain an origin of replication, which controls the host range and copy number of the plasmid.
Can bacteria survive without plasmids?
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The source read here, OpenStax Microbiology, says plasmids often carry advantageous traits such as antibiotic resistance and are important to the survival of the organism.
Going deeper
