The structure of nuclear pre-mRNA. VII. The hybridization and renaturation properties of double-stranded sequences of nuclear pre-mRNA]

Some properties of the double-stranded regions of pre-mRNA are discribed. 1. The double-stranded regions contain approximately 80 base pairs. 2. The material contains the heterogeneous populations of sequences and some homogenous material which renatures with a COT1/2 value of (1.5-3) X 10(-4). 3. Identical sequences of fast-renaturing "hairpins" may be found in various tissues. 4. Double-stranded RNA and mRNA have some sequences complementary to each other. These results consistent with the view that the hairpin sequences may act as specific recognition sites for ribonucleases involved in processing of pre-mRNA.     

Double-stranded regions in denatured DNA from mouse cells

Approximately 2% of the DNA of the mouse genome reassociates at infinitely low C ₀ t values, 10^-7 to 10^-6 moles 1^-1 s. The melting profile of the reassociation product, which is resistant to nuclease S₁ digestion, has been characterized by hydroxyapatite column chromatography. The properties of these nuclease resistant sequences suggest that they exist as DNA-hairpins and that they originate from reverted base sequences within the genome.     

Records on parasitoids of smaller poplar borer,Saperda populnea [Coleoptera,Cerambycidae] along the Danube in Bulgaria

During the period 1986–1988 the parasitoids of smaller poplar borer,Saperda populnea L. (Coleoptera, Cerambycidae) along the Danube in Bulgaria were studied. A total of 898 smaller poplar borer galls were investigated—289 in 1986, 404 in 1987, and 205 in 1988. In the particular years the parasitoids of smaller poplar borer namelyBillaea irrorata Meig.(Diptera, Tachinidae), Dolichomitus populneus Ratz. (Hym.: Ichneumonidae), andIphiaulax impostor Scop. (Hym.: Braconidae) destroyed from 13.1 up to 28.0% of the pest larvae, thus decreasing their frequency together with the other limiting factors by 56.1% up to 81.2%. The tachinid flyB. irrorata decreased the smaller poplar borer larvae frequency by 9.3% up to 18.9%, while the ichneumonoidD. populneus, and the braconoidI. impostor destroyed insignificant percentages of these larvae—0.5% up to 1.7% and 0.5% up to 2.5% resp. The flight period of the pest preceded or almost coincided with the ones ofD. populneus, andI. impostor. The flyB. irrorata always appeared last and its flight period was expanded.      

Detection of new genes participating in the trans-regulation of locus yellow of MDG-4 in Drosophila melanogaster

The aim of the present work was to obtain mutations in the genes involved in regulation of the yellow locus and mdg4. For this purpose, we searched for mutations changing phenotypic expression of the y(2) mutation induced by mdg4 insertion into the regulatory region of the yellow locus. Mutations have been obtained in the earlier described system of prolonged genome instability, sometimes combined with P-M hybrid dysgenesis. The mutation mod(mdg4) in a novel gene, modifier of mdg4, was detected which either enhanced or suppressed a phenotypic expression of several mutations induced by mdg4 insertion. We suggest that mod(mdg4) controls the expression of mdg4. In addition, the mutations in five loci located on the X chromosome have been found which enhanced the mutation phenotype of several y alleles induced by insertions of different mobile elements in the regulatory region of the latter. Possibly, the protein products of these genes designated as enhancers of yellow-1, 2, 3, 4 and 5 are directly or indirectly involved in control of the yellow locus expression.