title: Interspersion and transcription of repeated sequences of rat DNA.
abstract: Repetitive rat DNA reassociated to Cot=0.1 and deprived of "foldback" sequences showed close interspersion with unique sequences. As measured by electron microscopy, the average length of repetitive segments was about 600 +/- 400, and of unique segments 1800-3600 base pairs. Pyrimidine tracts over 80 nucleotides in length were found mainly in foldback and repetitive fractions. Oligo(dT) tracts, 20-30 bases in length prevailed in the DNA fraction reassociated to Cot=0.1. Repetitive and unique DNA fractions were annealed to Millipore filters and hybridized with hnRNA. Up to 1.6% of repetitive DNA reassociated to Cot=0.05 showed base complementarity with hnRNA, whereas the comparative figures for DNA reassociated to Cot=10 and for the unique fraction were 0.8% and 0.3% respectively. When hybridization of hnRNA was carried out in solution in vast DNA excess, no hybrid formation with repetitive sequences reassociated to Cot=0.1 was observed, although hybridization with DNA reassociated to Cot=10 was noticeable.
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism; D003851:Deoxyribonucleases; D004720:Endonucleases; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009693:Nucleic Acid Hybridization; D009695:Nucleic Acid Renaturation; D014158:Transcription, Genetic
chemical_list: D004270:DNA, Circular; D004247:DNA; D003851:Deoxyribonucleases; D004720:Endonucleases