Orangutans Harbor Ancient Primate Alu
Alu elements infiltrated the ancestral primate genome about 65 million years ago. Once gained an Alu element is rarely lost so comparison of Alu between species can be used to map primate evolution and diversity. New research published in BioMed Central’s open access journal Mobile DNA has found a single Alu, which appears to be an ancestral great ape Alu, that has uniquely multiplied within the orangutan genome.
Analysis of DNA sequences has found over a million Alu elements within each primate genome, many of which are species specific: 5,000 are unique to humans, while 2,300 others are exclusive to chimpanzees. In contrast the orangutan lineage only has 250 specific Alu. These tiny pieces of mobile DNA are able to copy themselves using a method similar to retroviruses. But, because this is an inexact process, a segment of ‘host’ DNA is duplicated at the Alu insertion sites and these footprints, known as ‘target site duplications’, can be used to ‘identify’ Alu insertions. Alu elements can be thought of as molecular fossils, and a shared Alu element sequence and location within the genome indicates a common ancestor.