transposable

Transposable refers to the property of elements that can move from one genomic location to another. In genetics, transposable elements (TEs) are DNA sequences that can change position within a genome, a process known as transposition. They were first demonstrated by Barbara McClintock in maize and were once called jumping genes.

Two major classes govern their movement: Class I retrotransposons move through an RNA intermediate and reverse transcription, while Class II DNA transposons move directly as DNA, often via a transposase that excises and inserts the element (cut-and-paste). Retrotransposons can be further categorized as long terminal repeat (LTR) elements and non-LTR elements (for example, LINEs and SINEs in mammals).

Transposable elements are pervasive in many organisms. In humans, transposable elements constitute roughly 45-50% of the genome. LINE-1 elements are autonomous and can mobilize themselves, while Alu elements are non-autonomous SINEs relying on other enzymes. Transposition can disrupt genes, alter expression, or create new regulatory elements, contributing to genome evolution and genetic disease.

Host genomes regulate TE activity by DNA methylation and histone modifications, and by RNA interference pathways such as piRNA. Over evolutionary time, TE insertions have been co-opted into gene regulatory networks and novel exons, shaping genome architecture.

Transposable elements remain a major area of genomics and evolution, offering insight into genome dynamics, mutation, and regulation.