The genomic location of rDNA in the rabbit was determined by in situ hybridization with ¹²⁵I-labeled ribosomal RNA (rRNA). The results demonstrate the presence of rRNA genes on chromosomes 13, 16, and 20, all of which have secondary constrictions, and on the telomere of the long arm of 21. The number of genes, as assessed by grain counts, was not equally distributed among the chromosomes. Chromosome 20 had the most copies and along with 13 and 16 carried significantly more genes than 21.

Nucleolar organizer regions (NOR's) were demonstrated in metaphase chromosomes of the domestic rabbit. Oryctolagus cuniculus (L.) (New Zealand white strain) using silver staining. Sequential quinacrine banding and a modification of the Ag-AS silver precipitation technique with duplicate photography allowed identification of silver staining NOR's on the short arms of chromosomes 13, 16, and 20, as well as the telomeric region of the long arms of number 21 in some cells. Chromosomes 13, 16 and 20 all have subterminal to terminal centromeres, often showed satellites and secondary constrictions, and were sometimes involved in associations.