Background: The sequencing of the human genome has revealed that almost half of the genome consists of interspersed repeats. Among the different types of interspersed repeats in humans, Alu elements are the most frequent ones, and new Alu elements are still integrated into new positions in the humane genome. In this review some consequences of this Alu activity are discussed. The first part of the review is focused on Alu element activity that causes genetic disease while the use of Alu elements as genetic tools for several purposes is discussed in the last part.
Materials and methods: This review article is based on a literature search on Medline.
Results and interpretation: Alu elements cause disease by two different mechanisms. A de novo insertion of an Alu element into, or close to, a gene may disrupt its normal function, while homologous recombination between two Alu elements may result in deletions or duplications that cause genetic disease. The high density of Alu elements in the human genome combined with their absence in non-primate species make them useful as genetic tools. Alu elements also represent "molecular fossils" that give phylogenetic information about primates as well as information about historical DNA rearrangements in the human genome.