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Related Concept Videos

Genome Size and the Evolution of New Genes03:21

Genome Size and the Evolution of New Genes

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While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.
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Transformation01:26

Transformation

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Microbial communities are dynamic environments where cell lysis releases free DNA into the surroundings. Other cells can take up this extracellular DNA through a process known as transformation.When a cell incorporates this foreign DNA into its genome, resulting in genetic modification, the process is known as transformation. Cells capable of this process are termed competent. Competence can be natural, as observed in certain bacteria and archaea, or artificially induced in the...
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Genomic DNA in Prokaryotes00:46

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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.
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DNA-only Transposons02:57

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DNA-only transposons are called autonomous transposons since they code for the enzyme transposase that is required for the transposition mechanism. Insertion of transposons can alter gene functions in multiple ways. They can mutate the gene, alter gene expression by introducing a novel promoter or insulator sequence, introduce new splice sites, and change the mRNA transcripts produced, or remodel chromatin structure.
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Plasmids01:28

Plasmids

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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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LTR Retrotransposons03:08

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LTR retrotransposons are class I transposable elements with long terminal repeats flanking an internal coding region. These elements are less abundant in mammals compared to other class I transposable elements. About 8 percent of human genomic DNA comprises LTR retrotransposons. Some of the common examples of LTR retrotransposons are Ty elements in yeast and Copia elements in Drosophila.
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Updated: Sep 12, 2025

Genome-wide Purification of Extrachromosomal Circular DNA from Eukaryotic Cells
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Genome-wide Purification of Extrachromosomal Circular DNA from Eukaryotic Cells

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Extrachromosomal Circular DNA: A Mobile Genetic Element Shaping Host Biology.

Shun Yao1, Oliver W Chung1, Ling Wang1

  • 1Department of Pharmacology & Cancer Biology, Duke University School of Medicine, Durham, North Carolina, USA;

Annual Review of Cell and Developmental Biology
|August 5, 2025
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Extrachromosomal circular DNA (ecDNA) acts as mobile genetic elements, driving genome evolution and adaptation. Understanding ecDNA

Keywords:
cancer evolutioncancer therapyecDNAgenome dynamicsmobile DNAviral ecDNA

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Area of Science:

  • Genetics
  • Molecular Biology
  • Genomics

Background:

  • DNA enables genetic information transmission, but sequences change for evolution.
  • Mobile genetic elements facilitate genome dynamics and adaptation.
  • Extrachromosomal circular DNA (ecDNA) is proposed as a novel class of mobile genetic elements.

Purpose of the Study:

  • To review the historical discoveries and conceptual evolution of ecDNA.
  • To categorize ecDNA forms, life cycle, and roles across organisms.
  • To highlight ecDNA's significance in physiology and pathology, and explore therapeutic strategies.

Main Methods:

  • Literature review of historical discoveries and conceptual evolution of ecDNA.
  • Categorization of ecDNA forms, biogenesis, maintenance, and clearance.
  • Discussion of ecDNA's roles in physiological processes and disease states.
  • Exploration of therapeutic strategies targeting ecDNA.

Main Results:

  • ecDNA represents a class of mobile genetic elements influencing genome dynamics.
  • ecDNA plays roles in development, stress adaptation, and evolution.
  • ecDNA is implicated in cancer progression, drug resistance, and viral infections.

Conclusions:

  • ecDNA significantly shapes host biology and genome dynamics.
  • ecDNA is a critical factor in physiological and pathological processes.
  • Targeting ecDNA offers a promising framework for biomedical interventions, particularly in oncology and antiviral treatments.