Characterization and Localization of the Human Genes for Ribosomal Ribonucleic Acid

Abstract

Summary: The genetic sequence complementary to ribosomal RNA was separated from human DNA and its characteristics studied. Both 18S and 28S sequences were located on the same isolated strand. DNA rRNA hybrids have a melting temperature of 80° or 4° less than that of native ribosomal DNA. Ribosomal genes behave as a satellite when complexed with Ag⁺ in the Cs₂SO₄ gradient. With in situ hybridization, these rRNA genes can be shown to chromosomally translocate. The study of a highly fluorescent chromosome indicates that the ribosomal DNA does not contribute to the fluorescent nature of the secondary constrictions. This study examines the molecular organization of human ribosomal genes. The chromosomal inheritance of these genes is explored by in situ hybridization. Speculation: Human ribosomal DNA represents a well defined repetitious DNA which can vary quantitatively in normal and abnormal ways. This DNA should be representative for studying the inheritance patterns of repetitious DNA.