Split Cell (IMAGE) University of Pennsylvania School of Medicine Caption Blotchy black regions of a wild type nucleus (left), which has normal amounts of the trimethyl-based chromatin compaction (denoted by black spots). Nucleus deficient in the enzymes (right), in which black blotchy parts indicative of highly compacted chromosomal regions are absent. Credit Dario Nicetto, Perelman School of Medicine, University of Pennsylvania 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.