The contribution of RNAs and retroposition to evolutionary novelties.

Retroposition is an ancient process dating back to the conversion of RNA to DNA genomes. Nevertheless, it continues to make tremendous structural and functional contributions to extant genomes. This process and the endurance, or even renaissance, of an RNA world in many lineages sheds a new light on the Central Dogma of Molecular Biology. The question of why reverse transcriptase has survived billions of years without an apparent cellular function is discussed. Retroposition constitutes one of the pervasive conflicts, in this case between host genome on one hand and mobile genetic elements on the other, that fuel the evolutionary process. It is obvious that retroposition has, thus far, contributed numerous useful novelties to genomes.