Mice with PER1 and PER2 Mutations (IMAGE) Salk Institute Caption Mice with a mutation in the PER2 gene (top right) have an altered sleep cycle, while those with a mutation in the PER1 gene (bottom right) have an abnormal eating schedule. Credit Satchidananda Panda 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.