Chromosome Crossroads (IMAGE) University of Pennsylvania School of Medicine Caption This is a human chromosome, with conventional nucleosomes containing the major form of the histones (green), and localization of the centromere histone H3 variant, CENP-A (red). Credit Ben E. Black, University of Pennsylvania School of Medicine 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.