Transposable elements are also called jumping genes, or transposons. They are a heterogeneous class of genetic elements that can insert at new locations on chromosomes. Transposons are classified into three major groups: Class I, retrotransposons; Class II, DNA transposons; Class III, miniature inverted-repeat transposable elements.
Structure and mechanism of transposons
Transposons have direct repeat flanking sequences that are not part of the transposons, and terminal inverted repeats that are part of the transposons. DNA transopsons translocate via a cut-and-paste mechanism, retrotransposons translocate via copy-and-paste mechanism.
Transposons in different organisms
Transposons exist in all organisms including bacteria. Bacteria transposons include two related classes: IS and Tn elements, both of which are DNA transposons. In Drosophila, P element is DNA transposon, while Copia and Gypsie are retrotransposons. Maize has many different types of transposons, including Ac/Ds elements (DNA transposon) and MITEs. Ty elements (retrotransposons) are well-studied in yeast.
Genetic effect of transposons
Because they move around the genome, transposons cause significant changes in genome organization and gene sequence. They can give insertion/deletion mutant and chromosomal inversion mutant. Transposons are used as tools in gene delivery or targeted mutation.