Mitochondrial pseudogenes: evolution's misplaced witnesses

Nuclear copies of mitochondrial DNA (mtDNA) have contaminated PCR-based mit ochondrial studies of over 64 different animal species. Since the last revi ew of these nuclear mitochondrial pseudogenes (Numts) in animals, Numts hav e been found in 53 of the species studied. The recent evidence suggests tha t Numts are not equally abundant in all species, for example they are more common in plants than in animals, and also more numerous in humans than in Drosophila. Methods for avoiding Numts have now been tested, and several re cent studies demonstrate the potential utility of Numt DMA sequences in evo lutionary studies. As relies of ancient mtDNA, these pseudogenes can be use d to infer ancestral states or root mitochondrial phylogenies. Where they a re numerous and selectively unconstrained, Numts are ideal for the study of spontaneous mutation in nuclear genomes.