ORGANIZATION OF THE 5S RIBOSOMAL-RNA GENE-CLUSTER IN THE HUMAN GENOME

The cluster of human 5S rRNA genes were mapped by in situ hybridizatio n to chromosome 1 locus q42.11-42.13, confirming the earlier literatur e data. Besides, an additional hybridization site was revealed at q43. The size of 5S rRNA single gene repeats and their genomic arrangement were determined by blot hybridization of fibroblast DNA fragments obt ained by agarose gel pulse-electrophoresis and electrophoresis of NotI , HindIII, BamHI, and AccI digests. The repeats were of three types: 2 .8 and 1.8 kb (HindIII), and 2.3 kb (BamHI); besides these, there were oligomers of 2-4 single repeats as well as uncleaved long stretches ( about a hundred kb) containing 5S DNA sequences. The data obtained sug gest a heterogeneous organization of 5S rRNA genes in the human genome .