Related Experiment Video
Updated: Jul 26, 2025
08:19
Generating Transposon Insertion Libraries in Gram-Negative Bacteria for High-Throughput Sequencing
Published on: July 7, 2020
10.5K
Ribosomal Intergenic Spacers Are Filled with Transposon Remnants.
Arnold J Bendich1, Scott O Rogers2
1Department of Biology, University of Washington, Seattle.
Genome Biology and Evolution
|June 21, 2023
Summary
Researchers mapped eukaryotic ribosomal DNA (rDNA) spacers, finding they contain short direct repeats (DRs) and long tandem repeats (TRs). These repetitive elements suggest spacers originated from transposon activity, influencing genome organization.
Area of Science:
- Molecular Biology
- Genomics
- Evolutionary Biology
Background:
- Eukaryotic ribosomal DNA (rDNA) consists of repeating units of conserved coding genes separated by variable spacer DNA.
- Previous rDNA maps had unannotated and inadequately studied spacer regions.
Purpose of the Study:
- To complete the rDNA maps by characterizing the sequences within the spacer regions.
- To investigate the origin and potential function of repetitive elements in rDNA spacers.
Main Methods:
- Comparative analysis of rDNA spacer sequences across 12 eukaryotic species.
- Identification and mapping of short direct repeats (DRs) and long tandem repeats (TRs) within spacers.
Main Results:
- All examined species' rDNA spacers were found to contain DRs and multiple TRs.
- External transcribed spacers also contained DRs and some TRs.
- The repetitive sequences suggest an origin from transposon insertion and imprecise excision.
Conclusions:
- The study provides complete rDNA maps by annotating spacer sequences.
- rDNA spacers likely serve to link transcription units and are favored sites for transposon activity due to their repetitive nature and high usage.
Related Concept Videos
03:08LTR Retrotransposons
17.6K
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...
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
17.6K
02:57DNA-only Transposons
14.6K
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...
The donor site from where the transposon is excised is either degraded or...
14.6K
03:18Non-LTR Retrotransposons
11.6K
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...
11.6K
01:24Transposons
66
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...
66
02:13Overview of Transposition and Recombination
15.9K
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...
15.9K
02:57piRNA - Piwi-interacting RNAs
6.9K
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...
6.9K