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LTR Retrotransposons

LTR Retrotransposons

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...

Non-LTR Retrotransposons

Non-LTR Retrotransposons

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...

Overview of Transposition and Recombination

Overview of Transposition and Recombination

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...

DNA-only Transposons

DNA-only Transposons

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...

Transposons

Transposons

Transposons, or "jumping genes," are small mobile genetic elements (MGEs) that range from 700 to 40,000 base pairs in length. They are found in all organisms and can move within the same chromosome or transfer to different chromosomes. In some cases, transposons can also jump between different host DNA molecules, such as plasmids or viruses, contributing to genetic variability.Barbara McClintock first discovered these mobile genetic elements in the 1940s while studying maize genetics, and she...

Retroviruses

Retroviruses

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: May 30, 2026

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

Published on: April 23, 2016

Retrotransposons that maintain chromosome ends.

Mary-Lou Pardue¹, P G DeBaryshe

¹Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. mlpardue@mit.edu

Proceedings of the National Academy of Sciences of the United States of America

|August 9, 2011

Summary

Drosophila utilize three retrotransposons to maintain telomeres instead of telomerase. These elements form arrays analogous to telomerase repeats, shaping and being shaped by the genome.

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Analysis of LINE-1 Retrotransposition at the Single Nucleus Level

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RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level

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Area of Science:

Genomics
Molecular Biology
Evolutionary Biology

Background:

The genus Drosophila lacks telomerase, the enzyme typically responsible for maintaining chromosome ends.
Telomeres in Drosophila are maintained by three specialized retrotransposons, which are mobile genetic elements that replicate via an RNA intermediate.

Purpose of the Study:

To investigate the unique mechanism of telomere maintenance in Drosophila.
To understand how retrotransposons have adapted to function at telomeres and shape the Drosophila genome.

Main Methods:

Comparative genomics analysis of telomere-specific retrotransposons across Drosophila species.
Molecular characterization of retrotransposon sequences and their integration patterns at chromosome ends.

Main Results:

Three non-long terminal repeat (non-LTR) retrotransposons are exclusively found at Drosophila telomeres.
These retrotransposons form long, head-to-tail arrays that are functionally and structurally analogous to telomerase-generated repeats.
Evidence suggests this telomere maintenance strategy evolved early in Drosophila evolution.

Conclusions:

Drosophila employs a unique retrotransposon-based system for telomere maintenance, highlighting genome plasticity.
Telomeric retrotransposons have co-evolved with the Drosophila genome, acquiring specialized features for their role in chromosome structure.