Hi, I am confused with NAD (Nucleolus associated chromatin domains) and NOR (Nucleolus organizer regions). NOR contain multiple copies of ribosomal RNA genes (rDNA) around which nucleoli form. They are located on the short arms of the acrocentric chromosomes (13, 14, 15, 21 and 22 in humans). These regions code for 5.8S, 18S, and 28S ribosomal RNA. NADs are primarily genomic regions with heterochromatic signatures and include transposable elements (TEs), sub-telomeric regions, and mostly inactive protein-coding genes. if you see the figure 3 of this paper "Genome organization in and around the nucleolus" or in this link http://www.ur.de/laengst/anemeth.html The NADs found in all chromosome but NOR found only in acrocentric chromosome. Overall nucleolus is the site of rRNA gene transcription, rRNA processing, and ribosome biogenesis. So my doubt is nucleolus forms due to NOR regions basically acrocentric chromosome then how NAD associated with all chromosome? Also, does anyone know the gtf file of chromosome position of NOR and NAD? Thanks.