Certain classes of interspersed repeat sequences propagate themselves by RNA mediated transposition; they have been called retrotransposons, and they constitute 25–40% of most mammalian genomes.
The shorter Alu or SINE repetitive DNA are specialized for uncoupling intrachromosomal gene conversion while the longer LINE repetitive DNA are specialized for uncoupling interchromosomal gene conversion.
In both cases, the interspersed repeats block gene conversion by inserting regions of non-homology within otherwise similar DNA sequences.
[3] By breaking the links that would otherwise overwrite novel DNA sequence variations, interspersed repeats catalyse evolution, allowing the new genes and new species to develop.
Insertion of an interspersed DNA element breaks this linkage, allowing independent evolution of a new gene.