THE RAT 5S RIBOSOMAL-RNA BONA-FIDE GENE REPEAT MAPS TO CHROMOSOME 19Q12-]QTER AND THE PSEUDOGENE REPEAT MAPS TO 12Q12

The bona fide 5S rRNA genes in the rat are found in a 1.8-kb tandem re peat and the pseudogenes occur in a 2.5-kb tandem repeat. Three bona f ide 5S rRNA genes and one gene variant with one base substitution in t he coding region were isolated from the 1.8-kb repeat. Six pseudogenes were isolated from the 2.5-kb repeat. The total number of genes/gene variants/pseudogenes is 700-1200 copies per haploid genome, and the ps eudogene repeat contains about 50% more 5S rDNA related sequences comp ared with the bona fide gene repeat. Various well-defined 5'- and 3'-f lanking sequences of the bona fide gene and of the pseudogene were use d for in situ hybridization to metaphase chromosomes. The results show ed that the bona fide 5S rRNA gene repeat Rn5s maps to chromosome 19q1 2 and the pseudogene repeat Rn5sp maps to 12q12.