These authors investigated the potential for errors in transcription to result in a heritable phenotypic change. They engineered the Escherichia coli lac repressor lacI to include sequences that result in transcription slippage. They then showed that, although a functional protein is produced, this error is able to result in a switch in the transcriptional circuit that LacI regulates. Furthermore, they show this switch to be heritable through generations. Thus, transcription encodes information that results in a heritable epigenetic change.