What is the Difference Between Transposon and Retrotransposon

The main difference between transposon and retrotransposon is that transposons or “jumping genes” or transposable elements (TE) are the DNA sequences that move from one location to another in the genome whereas retrotransposon or class 1 TE is a type of transposon that requires reverse transcription: the transcription of RNA into DNA.

Transposon and retrotransposon are two types of DNA sequences that change their location within the genome.

Key Areas Covered

1. What is Transposon
   • Definition, Structure, Classification
2. What is Retrotransposon
   • Definition, Structure, Classification
3. Similarities Between Transposon and Retrotransposon
   • Outline of Common Features
4. Difference Between Transposon and Retrotransposon
   • Comparison with Key Differences

Key Terms

Retrotransposon, Transposable Elements, Transposon

What is Transposon

Transposon or transposable elements (TE) AKA “Jumping genes” are types of DNA sequences that move within the genome of a particular organism: eukaryote or prokaryote. The geneticist Barbara McClintock of Cold Spring Harbor Laboratory in New York identified the transposable elements more than 50 years ago. These transposable elements generally occur in large numbers in the genome; approximately 50% of the human genome is made up of transposons.  More importantly, transposition results in a mutation at the landing site, determining the function of the transposable element. Therefore, some of these jumping genes can cause disease development in the organism. On the other hand, TEs can contain siRNAs for the mediation of their silencing. Transposons can also promote evolution by translocation.

Figure 1: DNA Transposon

However, transposons can be either autonomous or nonautonomous. Autonomous transposons move on their own but, nonautonomous transposons require the presence of another transposon for their transposition.  Moreover, nonautonomous transposons do not contain genes for transposase and reverse transcriptase.  The main classification method of transposons is their requirement of reverse transcription for the transposition. Class I TEs are retrotransposons that undergo reverse transcription while class 2 TEs are DNA transposons that do not undergo reverse transcription during transposition. Usually, DNA transposons are autonomous and encode transposase.

What is Retrotransposon

Retrotransposon or class 1 element is a type of transposable element that requires reverse transcription for transposition. However, retrotransposons move through the action of RNA intermediaries. Before inserting into the target site, they undergo reverse transcription back into DNA. They also do not encode for transposase. Furthermore, LTR TEs and non-LTR TEs are the two types of retrotransposons. In general, the main characteristic feature of LTR TEs is the presence of long terminal repeats (LTRs) on both ends.

Figure 2: Retrotransposon

 Moreover, Alu and L1 are two examples of non-LTR TEs. Usually, up to 15-17% of the human genome is made up of non-LTR TEs.

Similarities Between Transposon and Retrotransposon

• Transposon and Retrotransposon are two types of DNA sequences that move within the genome.
• Their function depends on their target site.
• They make up a large part of the human genome.

Difference Between Transposon and Retrotransposon

Definition

Transposon refers to a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell’s genetic identity and genome size, while retrotransposon refers to a type of genetic component that copies and pastes itself into different genomic locations (transposon) by converting RNA back into DNA through the reverse transcription process using an RNA transposition intermediate.

Also Known As

Transposons are also known as “jumping genes” or transposable elements (TEs) while retrotransposons are known as class 1 elements.

Reverse Transcription

DNA transposon does not undergo reverse transcription while retrotransposon undergoes reverse transcription.

Classification

DNA transposons and retrotransposons are the two types of transposons while LTR-TEs and non LTR-TEs are the two types of retrotransposons.

Conclusion

In brief, transposon and retrotransposon are two types of DNA sequences that move through the genome to target sites, initiating their functions. Furthermore, transposons make up a large portion of the human genome. DNA transposon and retrotransposon are two types of transposons. Retrotransposons move by reverse transcription. Therefore, the main difference between transposon and retrotransposon is the transposition by reverse transcription.

References:

1. Pray, L. (2008) Transposons: The jumping genes. Nature Education 1(1):204

Image Courtesy:

1. “DNA Transposon” By Mariuswalter – Own Work (CC BY-SA 4.0) via Commons Wikimedia
2. “Retrotransposons” By Mariuswalter – Own Work (CC BY-SA 4.0) via Commons Wikimedia