Within most gene catalogs, pseudogenes have been annotated as a byproduct of protein-coding gene annotation, since a transcript has been identified with a frameshift or deletion, rather than an important entity in its own right. However recent analysis of retrotransposed pseudogenes such at PTENP1 (Poliseno et al. 2010) and DHFRL1 (McEntee et al. 2011) have found some retransposed pseudogenes to be expressed and functional and to have major impacts on human biology. The GENCODE catalog is unique in its annotation of the comprehensive pseudogene landscape of the human genome using a combination of automated, manual, and, more recently, experimental methods.
