Alu repetitive sequences, also known as Alu elements or simply Alus, are a type of transposable element (TE) that is highly abundant in the human genome. Named after the restriction endonuclease that specifically recognizes and cleaves it, Alu elements are a subgroup of Short Interspersed Nuclear Elements (SINEs), one of the two major classes of TEs in humans.
Alu repetitive sequences are approximately 300 base pairs long and are interspersed throughout the human genome, occurring in millions of copies. They are derived from a small 7SL RNA gene that is normally part of a larger RNA molecule involved in protein synthesis. Over evolutionary time, these RNA molecules have been reverse transcribed and integrated back into the genome as Alu repetitive sequences.
Alus are considered "selfish" DNA elements, as they are incapable of encoding any proteins and are entirely parasitic in nature. Nonetheless, their abundance in the genome suggests that Alus have played a significant role in evolutionary processes. They have been implicated in genome evolution, including the creation of new exons, regulation of gene expression, chromosomal rearrangements, and genome instability.
Due to their repetitive nature, Alu elements can lead to genetic variations and genomic disorders. They have been linked to several genetic disorders, including certain cancers, neurodegenerative diseases, and genetic abnormalities. Studying Alu repetitive sequences is important for understanding the functional consequences of these elements and their impact on human biology and disease.
