Centromere (IMAGE) Max-Planck-Gesellschaft Caption Order in the nucleus: Centromeres (marked in green) of the 13 Drosophila tissue culture chromosomes are clustered at only three positions. They attach to the nuclear region called nucleolus (dark spot). Chromatin is stained in red and marks the nucleus. Credit Patrick Heun, MPI of Immunobiology and Epigenetics 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.