title: Heterochromatic DNA in Triturus (Amphibia, Urodela). I. A satellite DNA component of the pericentric C-bands.
abstract: We have studied the structure, genome organization, chromosomal location, conservation across species and transcription on lampbrush chromosomes, of an AT-rich satellite DNA component of the newt, Triturus vulgaris meridionalis. The satellite (Sat G), originally isolated by gradient centrifugation, represents about 2% of the vulgaris genome and comprises a highly repetitive sequence family (HindIII family), whose monomers have been cloned. The repeat units are about 330 bp long, as measured on gels, and a cloned unit (pTvm1) is 310 bp long, as shown by sequencing. Abundant clusters of the HindIII family sequences are located within the pericentric heterochromatin (i.e. the C-bands placed at both sides of, and at a certain distance from, the centromeres) in most chromosomes. Both the sequence family and its overall pattern of chromosomal distribution are conserved within the genus Triturus, despite a few species-specific differences. The great majority of the HindIII family sequences are unexpressed on lampbrush chromosomes; they reside within pericentric, condensed segments of the chromosome axis ("loopless bars"). Only a few sequences are transcribed on some loops, suggesting that transcription promotion does not depend on the satellite sequences themselves.
mesh_terms: D000557:Ambystoma / Q000235:genetics; D000818:Animals; D004262:DNA Restriction Enzymes; D004276:DNA, Satellite / Q000235:genetics* / Q000302:isolation & purification; D005260:Female; D006238:Haploidy; D006570:Heterochromatin / Q000032:analysis*; D007621:Karyotyping; D009337:Necturus / Q000235:genetics; D009693:Nucleic Acid Hybridization; D009865:Oocytes / Q000166:cytology; D010957:Plasmids; D012091:Repetitive Sequences, Nucleic Acid; D013045:Species Specificity; D014319:Triturus / Q000235:genetics*; D014981:Xenopus / Q000235:genetics
chemical_list: D004276:DNA, Satellite; D006570:Heterochromatin; D004262:DNA Restriction Enzymes