In what way might transposons contribute positively to evolution?

Transposons are mobile elements that are very important in the evolution of the eukaryotic genome. For example, transposons are involved in the formation of introns. Evolution often deactivates DNA transposons via RNA interference, leaving them as introns. They are also important in the production of antibody diversity via V(D)J recombination because the mechanism of this recombination is similar to that of some transposons (probably originated from it). Another advantage of these mobile elements is in the formation of interspersed repeats within genomes which are created by transposition. Because interspersed repeats block gene conversion, they protect novel gene sequences from being overwritten by similar gene sequences. Transposons can contain many types of genes.

Regular or uniform type