Chimera (EST)

In genetics, a chimera is a single cDNA sequence originating from two transcripts. It is usually considered to be a contaminant in transcript and expressed sequence tag (EST) databases. It is estimated that approximately 1% of all transcripts in the National Center for Biotechnology Information's Unigene database contain a "chimeric sequence".

Methods have been devised to detect them, such as the Ribosomal Database Project's CHECK_CHIMERA program. However, in protein engineering, "chimeragenesis (forming chimeras between proteins that are encoded by homologous cDNAs)" is one of the "two major techniques used to manipulate cDNA sequences".