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Related Concept Videos

Overview of Transposition and Recombination02:13

Overview of Transposition and Recombination

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Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in speciation by changing genome sizes and modifying gene expression patterns. For example, in bacteria, transposition can lead to conferring antibiotic resistance. Movement of transposable elements within the genetic pool of pathogenic bacteria can aid in transfer of antibiotic-resistant genetic elements. In eukaryotes, transposons can carry out...
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LTR Retrotransposons03:08

LTR Retrotransposons

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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.
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
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DNA-only Transposons02:57

DNA-only Transposons

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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.
The donor site from where the transposon is excised is either degraded or...
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Non-LTR Retrotransposons03:18

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As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
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piRNA - Piwi-interacting RNAs02:57

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PIWI-interacting RNAs, or piRNAs, are the most abundant short non-coding RNAs. More than 20,000 genes have been found in humans that code for piRNAs while only 2000 genes have been found for miRNAs. piRNAs can act at the transcriptional and post-transcriptional levels and have a vital role in silencing transposable elements present in germ cells. They are also involved in epigenetic silencing and activation. Previously, they were thought to function only in germ cells but new evidence suggests...
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Retroviruses02:33

Retroviruses

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Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
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Related Experiment Video

Updated: Oct 19, 2025

Real-Time Quantification of the Effects of IS200/IS605 Family-Associated TnpB on Transposon Activity
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Circular RNA repertoires are associated with evolutionarily young transposable elements.

Franziska Gruhl1,2, Peggy Janich2,3, Henrik Kaessmann4

  • 1SIB Swiss Institute of Bioinformatics, Lausanne, Switzerland.

Elife
|September 20, 2021
PubMed
Summary
This summary is machine-generated.

Circular RNAs (circRNAs) are surprisingly not conserved across species. Most circRNAs arise convergently, suggesting they are byproducts of gene regulation rather than functionally conserved elements.

Keywords:
circRNAevolutionevolutionary biologygeneticsgenomicshumanmammalsmouseratrhesus macaquesplicingtransposons

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Area of Science:

  • Genomics
  • Evolutionary Biology
  • Molecular Biology

Background:

  • Circular RNAs (circRNAs) are regulatory molecules involved in post-transcriptional gene regulation.
  • Their formation depends on specific RNA sequences that promote a circularization process.
  • Previous studies suggested conserved functions for circRNAs due to conserved gene structures.

Purpose of the Study:

  • To investigate the evolutionary conservation of circRNAs across mammalian species.
  • To determine if conserved circRNAs are under purifying selection.
  • To understand the genomic context and origins of circRNAs.

Main Methods:

  • Comparative analysis of circRNA repertoires across five mammalian species (marsupials, rodents, primates).
  • Examination of sequence conservation in exonic loci and splice sites of circRNA-producing genes.
  • Analysis of transposable elements associated with circRNA origins.

Main Results:

  • Few circRNAs originate from orthologous loci across all analyzed mammalian species.
  • CircRNAs from orthologous loci are linked to young, species-specific transposable elements.
  • Evidence suggests circRNA emergence is often a byproduct of transposon-driven splicing.

Conclusions:

  • Widespread functional conservation of circRNAs is unlikely.
  • Many circRNAs likely evolved convergently due to genomic features like transposon insertions.
  • CircRNA evolution appears to be largely species-specific rather than anciently conserved.