Retrotransposon

Retrotransposons (also called transposons via RNA intermediates) are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms. They are one of the two subclasses of transposon, where the other is DNA transposon, which does not involve an RNA intermediate. They are particularly abundant in plants, where they are often a principal component of nuclear DNA. In maize, 49–78% of the genome is made up of retrotransposons. In wheat, about 90% of the genome consists of repeated sequences and 68% of transposable elements. In mammals, almost half the genome (45% to 48%) is transposons or remnants of transposons. Around 42% of the human genome is made up of retrotransposons, while DNA transposons account for about 2–3%.

Biological activity

The retrotransposons' replicative mode of transposition by means of an RNA intermediate rapidly increases the copy numbers of elements and thereby can increase genome size. Like DNA transposable elements (class II transposons), retrotransposons can induce mutations by inserting near or within genes. Furthermore, retrotransposon-induced mutations are relatively stable, because the sequence at the insertion site is retained as they transpose via the replication mechanism.