title: 3 micron DNA - an extrachromosomal ribosomal DNA in the yeast Saccharomyces cerevisiae.
abstract: A new class of extrachromosomal DNA which consists predominantly of covalently closed molecules with lengths around 3 micron, has been detected in Saccharomyces cerevisiae strain 6-1G-P188 from the Peterhof collection. Restriction analysis of the 3 micron DNA as well as of recombinant plasmids carrying HindIII fragments of the 3 micron DNA permitted construction of a physical map of the new extrachromosomal DNA species, and detection of two types differing by one EcoRI restriction site. Molecular hybridization, as well as comparison of the restriction maps, revealed the complete structural identity of the 3 micron DNA with a chromosomal repetitive unit of rDNA containing the genes for 25 S, 18 S, 5.8 S and 5 S rRNAs.
mesh_terms: D002874:Chromosome Mapping; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics*; D005111:Extrachromosomal Inheritance; D005796:Genes; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D012335:RNA, Ribosomal / Q000235:genetics*; D011995:Recombination, Genetic; D012270:Ribosomes / Q000648:ultrastructure*; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D012335:RNA, Ribosomal; D004262:DNA Restriction Enzymes