Chimeric cDNA clones : a novel PCR artifact

During the cloning of a transcript of one member of a closely related gene family, the human gamma -crystallin gene family, we encountered a novel artifact of the polymerase chain reaction: the formation of chimeric cDNA molecules. Our experimental strategy in cloning the human gamma E-crystallin transcript was a common one: first strand cDNA synthesis on human lens RNA using AMV reverse transcriptase and a gamma E specific primer followed by PCR with the same gamma E specific primer as reverse primer and a common gamma -crystallin forward primer.