A physical map of the ribosomal DNA repeat unit of Aspergillus nidulans

The ribosomal DNA repeat unit of Aspergillus nidulans has been cloned in pBR322 and a restriction map constructed. The genes coding for the 17S, 5.8S and 25S rRNAs are found in blocks separated by a 1.7 kb spacer region, with the 5.8S RNA gene lying between the genes for the two larger RNAs. The total length of the repeat unit is 7.7 kb. The 5S rRNA is not present in the repeat unit.