Genome structure of Tetrahymena pyriformiis
- 1 January 1978
- journal article
- research article
- Published by Springer Nature in Chromosoma
- Vol. 69 (3) , 275-289
- https://doi.org/10.1007/bf00332132
Abstract
Reassociation kinetics of DNA from the macronucleus of the ciliate, Tetrahymena pyriformis GL, has been studied. The genome size determined by the kinetic complexity of DNA was found to be 2.0×108 base pairs (or 1.2×1011 daltons). About 90% of the macronuclear DNA fragments 200–300 nucleotides in length reassociate at a rate corresponding to single-copy nucleotide sequences, and 7–9% at a rate corresponding to moderate repetitive sequences; 3–4% of such DNA fragments reassociate at C0t practically equal to zero. To investigate the linear distribution of repetitive sequences, DNA fragments of high molecular weight were reassociated and reassociation products were treated with Sl-nuclease. DNA double-stranded fragments were then fractionated by size. It has been established that in the Tetrahymena genome long regions containing more than 2000 nucleotides make up about half of the DNA repetitive sequences. Another half of the DNA repetitive sequences (short DNA regions about 200–300 nucleotides long) intersperse with single-copy sequences about 1,000 nucleotides long. Thus, no more than 15% of the Tetrahymena genome is patterned on the principle of interspersing single-copy and short repetitive sequences. Most of the so called “zero time binding” or “foldback” DNA seem to be represented by inverted self-complementary (palindromic) nucleotide sequences. The conclusion has been drawn from the analysis of this fraction isolated preparatively by chromatography. About 75% of the foldback DNA is resistant to Sl-nuclease treatment. The Sl-nuclease resistance is independent of the original DNA concentration. Heat denaturation and renaturation are reversible and show both hyper and hypochromic effects. The majority of the inverted sequences are unique and about 20% are repeated tens of times. According to the equilibrium distribution in CsCl density gradients the average nucleotide content of the palindromic fraction does not differ significantly from that of total macronuclear DNA. It was shown that the largest part of this fraction of the Tetrahymena genome are not fragments of ribosomal genes.Keywords
This publication has 25 references indexed in Scilit:
- EVOLUTION OF MACRONUCLEAR ORGANIZATIONAnnual Review of Genetics, 1976
- Free ribosomal DNA molecules from Tetrahymena pyriformis GL are giant palindromesJournal of Molecular Biology, 1976
- The macronuclear ribosomal DNA of Tetrahymena pyriformis is a palindromeJournal of Molecular Biology, 1976
- Evolutionary divergence and length of repetitive sequences in sea urchin DNAJournal of Molecular Evolution, 1976
- Structural organization of the genome of the cellular slime mold dictyostelium discoideum: Interspersion of repetitive and single-copy DNA sequencesCell, 1975
- Palindromic base sequences and replication of eukaryote chromosome endsNature, 1974
- Interspersion of repetitive and non-repetitive DNA sequences in the sea urchin genomeCell, 1974
- Palindromes in chromosomesJournal of Molecular Biology, 1974
- The Amount of Ribosomal RNA Genes in Tetrahymena pyriformis in Different Physiological StatesEuropean Journal of Biochemistry, 1972
- Kinetics of renaturation of DNAJournal of Molecular Biology, 1968