Pseudogene: lessons from PCR bias, identification and resurrection.

Pseudogenes are fragments of non-functional genomic DNA with high sequences similarity to normal functional genes. They are a kind of non-coding DNA produced by gene duplications or retrotranspositions. Pseudogenes exist in human genome at a large quantity which is nearly as much as that of normal functional genes. They could cause PCR bias in molecular biology experiments and confuse related analysis. On the other hand, pesudogenes are important elements in genomics study for getting an integral picture of genome annotation. They give diverse information of evolutionary history and are regarded as genome fossils. Worldwide research project "encyclopedia of DNA elements"(ENCODE) founded in recent years have enhanced our understanding of pseudogenes. Approaches established to identify pseudogenes include PseudoPipe, HAVANA method, PseudoFinder, RetroFinder, GIS-PET method and consensus method. This paper discuss pseudogenes with respect to the formation mechanisms, distribution, and problems for PCR, importance and identification of pseudogenes. Furthermore, potential resurrection of pseudogenes and their potential function are discussed.