Photoreceptors Cells (IMAGE) Université de Genève Caption Photoreceptors cells responsible for colour vision. By sequencing one cell at a time, the researchers identified a gene (Rbp4) present in a small number of cells (in green). In purple, photoreceptors in which the Rbp4 gene is not activated. Credit © UNIGE, Pierre Fabre Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.