title: Anucleolate frog embryos contain ribosomal DNA sequences and a nucleolar antigen.
abstract: Previous studies of Xenopus laevis embryos homozygous for the nucleolar deletion mutation have concluded that these embryos contain few, if any, copies of the genes for the 18 S and 28 S ribosomal RNAs. Using hybridization to restriction endonuclease digests of DNA it is found, in fact, that a small amount of ribosomal DNA is still present in such embryos. The ribosomal DNA in these embryos appears to include a few normal repeats together with a variety of unusual fragments containing either spacer or gene sequences. An antibody found in the serum of a scleroderma patient reacts with an antigen localized in the nucleoli of wild-type embryos. In anucleolate embryos this antigen is found in the so-called pseudonucleoli and in many small bodies in the nuclei.
mesh_terms: D000818:Animals; D000941:Antigens / Q000032:analysis*; D001323:Autoantibodies; D001483:Base Sequence; D002466:Cell Nucleolus / Q000276:immunology / Q000502:physiology*; D004247:DNA / Q000378:metabolism*; D004262:DNA Restriction Enzymes; D005455:Fluorescent Antibody Technique; D006801:Humans; D009154:Mutation; D009693:Nucleic Acid Hybridization; D012270:Ribosomes / Q000378:metabolism*; D012595:Scleroderma, Systemic / Q000276:immunology; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics
chemical_list: D000941:Antigens; D001323:Autoantibodies; D004247:DNA; D004262:DNA Restriction Enzymes