Retrotransposon

Retrotransposon is a type of transposable element that can amplify itself in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. They are a subclass of transposons. They are particularly abundant in plants, where they are often a major component of nuclear DNA. In maize, 49–78% of the genome is made up of retrotransposons. In wheat, about 90% of the genome is composed of repeated sequences such as retrotransposons. In mammals, nearly half the genome (45%) is composed of retrotransposons. Retrotransposons are also known as "Class I" transposons, due to their mechanism of transposition, which involves reverse transcription of the element's RNA transcript into DNA by a reverse transcriptase enzyme.

Etymology

The term "retrotransposon" was derived from the Latin word "retro", meaning backwards, and "transposon", which is a segment of DNA that can move to different positions within a genome.

Types of Retrotransposons

Retrotransposons are categorized into two types: LTR (Long Terminal Repeat) retrotransposons and non-LTR retrotransposons.

LTR Retrotransposons

LTR retrotransposons have direct repeats at both ends that play a role in transposition. The name "LTR retrotransposon" comes from the characteristic structure of these sequences, which are long terminal repeats (LTRs) at both ends.

Non-LTR Retrotransposons

Non-LTR retrotransposons can be further divided into two main types: LINEs (Long Interspersed Nuclear Elements) and SINEs (Short Interspersed Nuclear Elements).

LINEs

LINEs are long DNA sequences that are transcribed into RNA, reverse transcribed into DNA, and then inserted at a new site in the genome. They are typically 6,000-8,000 base pairs long.

SINEs

SINEs are short DNA sequences that are also transcribed into RNA, reverse transcribed into DNA, and then inserted at a new site in the genome. They are typically 100-400 base pairs long.

Related Terms

• Transposon
• Eukaryotic
• Nuclear DNA
• Reverse Transcriptase

Retrotransposon Resources
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