transposons

Transposons, also known as transposable elements or "jumping genes," are DNA sequences capable of changing their position within a genome. These mobile genetic elements can move from one location to another, either via a "cut and paste" mechanism or through an "copy and paste" process, often resulting in genetic variation.

Transposons were first discovered in maize by Barbara McClintock in the 1940s, a finding that earned her the Nobel Prize in Physiology or Medicine in 1983. They are present in the genomes of many organisms, including bacteria, plants, and animals, and can constitute a significant portion of the genome. For example, transposons make up nearly 45% of the human genome.

There are two main classes of transposons. Class I elements, or retrotransposons, replicate via an RNA intermediate, using reverse transcription to insert copies back into the genome. Class II elements, or DNA transposons, move directly as DNA through a "cut and paste" mechanism facilitated by the enzyme transposase. Some transposons have regulatory roles, influence gene expression, or induce mutations, contributing to genetic diversity and evolution.

While transposons can be beneficial by promoting genetic diversity and adaptation, they may also pose risks by disrupting gene function or causing genomic instability. Organisms have evolved mechanisms, such as DNA methylation and RNA interference, to suppress transposon activity and maintain genomic integrity.

Overall, transposons are integral to genome dynamics, playing a complex role in genetic variation, evolution, and genome structure across diverse species.