What is the difference between a plasmid and a transposon?

A plasmid is a self-replicating DNA molecule, usually circular, that exists separately from the chromosome. A transposon is a segment of DNA that moves from one location to another within or between DNA molecules, including chromosomes and plasmids, rather than replicating independently.

Plasmids and Mobile Genetic Elements

Plasmids and other mobile genetic elements are pieces of DNA that replicate or move semi-independently of the chromosome, carrying accessory genes and reshaping bacterial genomes.

Definition

Mobile genetic elements are DNA segments that can move within or between genomes or replicate independently of the chromosome, including plasmids, transposons, insertion sequences, and integrons.

Scope

This topic covers plasmids and their replication, copy-number control, and classification; resistance and virulence plasmids; transposons and insertion sequences that move within and between DNA molecules; integrons that capture gene cassettes; and the role of these elements in genome plasticity and the spread of adaptive traits. It also notes the use of plasmids as cloning and expression vectors.

Core questions

How do plasmids replicate and remain stable in a population?
How do transposons and insertion sequences move within genomes?
Why are mobile elements important for the spread of resistance?
How are plasmids exploited as tools in genetic engineering?

Key concepts

Plasmid replication and copy number
Resistance and virulence plasmids
Transposons and insertion sequences
Integrons and gene cassettes
Plasmids as cloning vectors

Mechanisms

Plasmids are usually circular DNA molecules that replicate using their own origins and partition into daughter cells, sometimes encoding transfer functions for conjugation. Transposons and insertion sequences move by recombination mechanisms that excise and reinsert the element or copy it to a new location, often carrying accessory genes with them. Integrons capture and express gene cassettes, helping assemble arrays of resistance determinants.

Clinical relevance

Mobile genetic elements are key vehicles for the spread of antibiotic resistance and virulence genes among bacteria, and engineered plasmids serve as the standard vectors for introducing and expressing genes in molecular biology and biotechnology.

History

Barbara McClintock's discovery of transposable elements in maize in the mid-twentieth century revealed that genetic elements can move within genomes, a concept later extended to bacteria, where plasmids and transposons were found to drive the spread of antibiotic resistance.

Key figures

Barbara McClintock
Joshua Lederberg

Seminal works

madigan2018
willey2020

Frequently asked questions

What is the difference between a plasmid and a transposon?: A plasmid is a self-replicating DNA molecule, usually circular, that exists separately from the chromosome. A transposon is a segment of DNA that moves from one location to another within or between DNA molecules, including chromosomes and plasmids, rather than replicating independently.