Abstract
Traditionally, pseudogenes have been regarded as "dead" gene copies as a result of features such as the absence of promoters and the existence of premature stop codons. However, the recognition of a truly disabled gene is not as straightforward as once believed. It is now known that promoters may be cryptic. Genomic recoding processes can allow for the synthesis of a peptide despite the present of premature stop codons. Alternative splicing can allow for the omission of exons that contain premature stop codons. Finally, negative evidence for pseudogene expression, for the relatively few pseudogenes for which it is available, must be interpreted with caution. This is in view of the fact that many genes express themselves only under very restricted conditions.