0000000000949081
AUTHOR
A.m. Pirrone
rDNA (18S-28S and 5S) co-localization and linkage between ribosomal genes and (TTAGGG)n telomeric sequence in the earthworm Octodrilus complanatus (Annelida: Oligochaeta: Lumbricidae) revealed by single- and double-colour FISH
Spermatogonial and metaphase I chromosomes of the lumbricid earthworm Octodrilus complanatus (Annelida: Oligochaeta) were examined using fluorescent in situ hybridization (FISH) with three repetitive DNA probes-5S rDNA, 18S-26S rDNA, and (TTAGGG)(n). Single-color FISH consistently mapped one chromosome pair per spread using either 5S rDNA or 18S-26S rDNA as probes. Simultaneous (18S-26S)-5S and (18S-26S)-(TTAGGG)(n) FISH demonstrated that repeated units of the two ribosomal families were overlapped and closely associated with telomeric sequences.
Heat-Shock Proteins in Sea Urchin Embryos
The production of heat-shock proteins in sea urchin embryos is accompanied by the appearance at the polysomal level of their relative mRNAs, as shown by their translation in a cell-free system; thus suggesting that the regulation of their production occurs at a transcriptional level. The mechanism for the inhibition of the bulk protein synthesis and for its reversal on the other hand should be looked for at a posttranscriptional level, since both these phenomena occur also in the presence of actinomycin D. The heat-shock proteins produced as early as at the mesenchyme blastula stage persist within the embryo at least till the pluteus stage.
Synthesis of RNA in isolated nuclei of sea urchin embryos.
It is demonstrated that isolated nuclei of sea urchin embryos are able to incorporate radioactive nucleotides into RNA. Some properties of the incorporation system are described.