Chromosomal localization of the major and 5S rRNA genes in the European eel (Anguilla anguilla).

The major (18S, 5.8S, and 28S) and 5S rRNA genes have been mapped by double fluorescent in situ hybridization to European eel metaphase chromosomes. The major rRNA genes were localized to a submetacentric pair of chromosomes that showed a consistent size polymorphism among the individuals studied. The 5S rRNA genes were clustered in a single locus that mapped to the centromeric region of an acrocentric pair. In contrast to the major rRNA genes, no detectable polymorphism, in either size or intensity of the fluorescent signal, was observed. The chromosomal organization of both families of rRNA genes are discussed in terms of genomic organization and chromosomal evolution.