Alu family

Alu family A group of closely related DNA sequences arising from a single ancestral sequence (see gene family) and found dispersed and repeated many times within the genome of humans and other primates. Full-length Alu sequences are about 280 bp long, and many are cleaved by the restriction enzyme AluI (hence the name). The human haploid genome contains roughly 500 000 full-length copies of Alu, plus many partial Alu sequences, making it the most abundant single sequence in the entire genome and constituting a large proportion of the class of moderately repetitive DNA known as SINEs. Alu sequences occur in the nontranslated regions (introns) of genes and between genes and probably have no function. They are retrotransposons and can thus replicate themselves. The variations in structure and distribution of Alu sequences among primates can be used both to help track the evolutionary history of the genome and as genetic markers (see marker gene) for physical mapping.