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Related Concept Videos

Genomic DNA in Prokaryotes00:46

Genomic DNA in Prokaryotes

49.0K
The genome of most prokaryotic organisms consists of double-stranded DNA organized into one circular chromosome in a region of cytoplasm called the nucleoid. The chromosome is tightly wound, or supercoiled, for efficient storage. Prokaryotes also contain other circular pieces of DNA called plasmids. These plasmids are smaller than the chromosome and often carry genes that confer adaptive functions, such as antibiotic resistance.
Genomic Diversity in Bacteria
Although bacterial genomes are much...
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Plasmids01:28

Plasmids

3.1K
Plasmids are extrachromosomal DNA molecules found in bacteria, archaea, and some eukaryotic microbes like yeast. These small, circular DNA structures typically contain fewer than 30 genes, although some may exist linearly. Plasmids vary in their number within a cell, known as copy number. Single-copy plasmids are present in one copy per cell and multi-copy plasmids are present in multiple copies, reaching over 100 copies per cell.Plasmids usually replicate independently of the chromosomal DNA...
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Eukaryotic Evolution01:24

Eukaryotic Evolution

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The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...
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Bacterial Transformation01:33

Bacterial Transformation

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In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.
Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
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Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes02:16

Comparing Mitochondrial, Chloroplast, and Prokaryotic Genomes

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The present-day mitochondrial and chloroplast genomes have retained some of the characteristics of their ancestral prokaryotes and also have acquired new attributes during their evolution within eukaryotic cells. Like prokaryotic genomes, mitochondrial and chloroplast genomes neither bind with histone-like proteins nor show complex packaging into chromosome-like structures, as observed in eukaryotes. Unlike mitotic cell divisions observed in eukaryotic cells, mitochondria and chloroplasts...
17.1K
Replication in Prokaryotes01:32

Replication in Prokaryotes

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DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the single origin of replication (ori) on the cell's circular chromosome. Replication then proceeds around the entire circle of the chromosome in each direction from the two replication forks, resulting in two DNA molecules.
Many Proteins Work Together to Replicate the Chromosome
Replication is coordinated and carried out by a host of specialized...
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Related Experiment Video

Updated: Feb 20, 2026

Detection of Horizontal Gene Transfer Mediated by Natural Conjugative Plasmids in E. coli
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Detection of Horizontal Gene Transfer Mediated by Natural Conjugative Plasmids in E. coli

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Origin and evolution of plasmids

C I Kado1

  • 1Davis Crown Gall Group, University of California 95616, USA.

Antonie Van Leeuwenhoek
|May 29, 1998
PubMed
Summary

Plasmids exhibit selfish and promiscuous DNA behavior, evolving from simple replicons to complex genetic engineering tools. Their ability to adapt hosts ensures their own survival in diverse environments.

Area of Science:

  • Molecular Biology
  • Evolutionary Biology
  • Genetics

Background:

  • The origin and evolution of plasmids offer insights into the fundamental nature of DNA.
  • Early nucleic acids, like oligoribonucleotides, demonstrated self-propagation and parasitic behavior, exemplified by satellite nucleic acids.
  • Viral RNA ribozymes show primitive RNA synthesis and polymerization capabilities without proteins.

Purpose of the Study:

  • To explore the evolutionary trajectory of plasmids from simple replicons to sophisticated genetic elements.
  • To understand the 'selfish' and 'promiscuous' nature of plasmids in relation to host survival and adaptation.
  • To highlight the conserved replication origins between viruses and plasmids.

Main Methods:

  • Comparative analysis of replication origins in virions and plasmids.

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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach

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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
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Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance

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Last Updated: Feb 20, 2026

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Detection of Horizontal Gene Transfer Mediated by Natural Conjugative Plasmids in E. coli

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Quantification of Plasmid-Mediated Antibiotic Resistance in an Experimental Evolution Approach
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  • Examination of plasmid-mediated genetic engineering of host cells for environmental adaptation.
  • Case studies of complex plasmids like Ti plasmid and pSym plasmids.

    • Main Results:

    • Replication origins are conserved, evolving from simple autocatalytic replicons to complex rolling circle mechanisms.
    • Plasmids genetically engineer hosts to survive hostile environments, ensuring their own perpetuation.
    • Plasmids sequester genes and acquire new ones, increasing host sophistication and adaptability.

    Conclusions:

    • Plasmids demonstrate a sophisticated evolutionary strategy, prioritizing their survival through host manipulation and adaptation.
    • The acquisition of genes by plasmids reflects increasing complexity and the ability to colonize new niches.
    • Examples like Ti and pSym plasmids showcase the advanced capabilities of evolved replicons.