EFFECTS OF ALU INSERTIONS ON GENE-FUNCTION

Alu elements are a family of short interspersed repetitive elements (S INEs) found exclusively in primates. These elements are around 300 bas e pairs long, are found in excess of one million copies per diploid ge nome, and are dispersed throughout the human genome. Alu elements are scattered by a mechanism called ''retrotransposition''. Three independ ent steps are involved in retrotransposition: transcription of the Alu repetitive element, reverse transcription of the Alu RNA and integrat ion of the Alu cDNA. The fact that Alu elements retrotranspose so read ily suggests that they have a myriad of effects on the genome, mostly by inactivating genes or altering their function. These characteristic s of Alu repetitive elements point to these repetitive DNA fragments a s a major driving force for evolution. In addition, Alu elements are k nown to adopt diverse functions depending on the context of the surrou nding genetic material into which they insert. In this article, we rev iew some of the evidence that demonstrates the functional significance of Alu repeats.