 They may be pseudogenes of coding genes or of non-coding RNA and may be whole or fragments of a gene and may or may not express a transcript.The boundary between what is considered a "reasonable" coding transcript is sometimes subjective as, in the absence of other evidence, the use of weak splice sites or short exons can often produce a putative, though unsatisfactory, model of a CDS.Pseudogenes and genes with a problematic structure are constantly under review in WormBase and new evidence is used to try to resolve their status.