Transposable Genetic Elements

Are TEs simply genomic parasites, or have they had a major impact on the evolution of species? Certainly, a TE integration could have an immediate detrimental impact on its host. However, specific and cumulative integrations may provide a mechanism for speciation. Drosophila P elements have been implicated in generating a reproductive barrier between strains. When females devoid of active elements are crossed with males of a strain with active elements, the TEs run rampant in developing germ-line cells, yielding various chromosomal anomalies and F₁ hybrid sterility. This may be an important mechanism in promoting the creation of new species from those strains.

Arguably, SINEs and LINEs may also drive species evolution through several mechanisms. They can disrupt or reset coordinated gene regulation, facilitate the pairing of homologous chromosomes, and possibly offer sites for genomic imprinting. In addition to individual integrations, LINEs have contributed to genomic diversity by delivering adjacent sequences, including whole genes, to new genomic locations. TEs also offer numerous sites for homologous unequal recombination.