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At least 19 recordsLinked to original sources
PubMed1977

[Genetic tolerance to alcohol in Drosophila: comparison of the effects of selection in D. melanogaster and D. simulans].

A strain of D. simulans and 3 strains of D. melanogaster having different initial levels of alcohol tolerance were submitted to increasing selection for at least 30 generations. In melanogaster, the relative efficiency of selection was inversely related to the initial level. In simulans, whose natural tolerance is particularly low, only a small increase was obtained. In all cases, tolerance increased progressively and could be considered as a quantitative character. These results are probably due to modifier genes of the alcohol dehydrogenase locus.

Alcohol Oxidoreductases↗
PubMed1979

Satellite Ic: a possible link between the satellite DNAs of D. virilis and D. melanogaster.

In this study, we isolated and characterized a previously undetected cryptic satellite DNA comprising 0.1% of the total nuclear genome of D. virilis. This satellite is hidden from detection in neutral CsCl by satellite I and is therefore designated cryptic satellite I or Ic. Sequence analysis reveals that Ic is the repeating heptanucleotide [poly d(AATATAG): d(CTATATT)]. It is more closely related to the three simple sequence satellite DNAs of D. melanogaster, a distantly related species, than it is to any of the major D. virilis satellite DNA sequences. Ic may therefore be a link between the simple sequence satellites of D. virilis and D. melanogaster. As an extension of this theory, we have constructed a "family tree" linking the satellites of D. virilis and D. melanogaster by a series of "simple" operations. Only one intermediate required by this evolutionary scheme has not yet been identified.

Animals↗
PubMed1979

Post-replicative nonribosomal transcription units in D. melanogaster embryos.

We have analyzed transcription units from D. melanogaster embryos in which most cells were in either the late S or the G2 phase of a synchronous cell cycle. Much of the chromatin of these embryos was observed in the form of parallel strands which appear to be newly replicated sister chromatids (McKnight and Miller, 1977). Lateral ribonucleoprotein (RNP) fibers were commonly observed attached to chromatin strands and are believed to be nascent transcripts. Very similar lateral fiber arrays were found on sister chromatid strands. Such paired, post-replicative RNP fiber arrays offer a unique opportunity to compare the transcription patterns on two copies of the same transcription unit. Analyses of paired transcription units yield the following conclusions. Transcription initiation and termination sites are the same for both copies of each transcription unit. Each transcription unit has a characteristic and constant RNP fiber frequency, and the fiber frequency is identical for both copies of the transcription unit. Active transcription units can have internal, fiber-free gaps which may result from interruptions in initiation of transcription. Transcription units differing in polarity and fiber frequency can occur in immediate juxtaposition. The relevance of these findings to eucaryotic transcriptional control mechanisms are discussed.

Animals↗
PubMed1979

rDNA magnification in D. melanogaster: state of rDNA copies following the first step.

D. melanogaster males of XYbb/O genetic constitution undergoing rDNA magnification were mated singly to XXbb+/O females, yielding XYbb/O male progeny, and to XNO- w sn bb+ females, yielding XYbb/XNO- females. The male and female offspring were scored for the bb+ phenotype. Results show that there is a higher percentage of bb+ flies in the XYbb/O male progeny than in XYbb/XNO- female progeny, in single crosses as well as in the combined data. rRNA/DNA hybridization experiments agree with this observation, by showing that the rDNA content in the progeny of premagnified flies was higher in the sons than in the daughters. These data indicate that the increase of ribosomal RNA genes is not due to a stable event such as an unequal mitotic sister exchange, whereas they do not contrast with the extracopy model.

Animals↗
PubMed1979

Genes for the 70,000 dalton heat shock protein in two cloned D. melanogaster DNA segments.

Two hybrid plasmids, 56H8 and 132E3, which contain D. melanogaster (Dm) DNA segments coding for the 70,000 dalton heat shock protein, have been isolated (Schedl et al., 1978). The analysis of the sequence arrangement presented in the accompanying paper (Moran et al., 1979) shows that both Dm segments contain homologous regions composed of three distinct sequence elements which together define a common unit. We report here that the sequences complementary to the 70,000 dalton protein mRNA appear to be confined to a major portion of the largest element of the common unit and that the other sequence elements are located at the 5' end of the gene. We have also determined the cytogenetic location of the 70,000 dalton protein genes and have investigated whether these sites are transcriptionally active in salivary gland chromosomes.

Animals↗
PubMed1979

Patterns of reversion to bobbed condition of magnified bobbed loci in D. melanogaster.

The number of genes coding for the ribosomal RNA (rDNA) can increase in D. melanogaster by means of a process called magnification. In this way, a partial deletion in this locus, termed bobbed, can reach a wild type condition. A newly magnified locus, in turn, reverts to a deficient bobbed condition if it is kept in a phenotypically wild type genotype for several generations. We studied bobbed loci at different magnification steps, analysing their behaviour through the reversion process and the way they carry out a second round of magnification. Results based on the analysis of the reversion process led to the conclusion that magnification consists of a progressive integration into the bobbed locus of free rDNA copies. Moreover, evidence is supplied that the extent of this integration affects the way a reverted locus goes through a second magnification cycle. The extensive characterization of reverted bobbed loci lends substantial support to the extra copies model of rDNA magnification.

Animals↗
PubMed1979

Alpha-amanitin-resistant D. melanogaster with an altered RNA polymerase II.

Following EMS mutagenesis we recovered a mutant of D. melanogaster that grows at concentrations of alpha-amanitin lethal to wild-type. To our knowledge this mutant represents the first example of an amanitin-resistant eucaryotic organism. The amanitin resistance of the mutant (AmaC4) is due to an alteration in its DNA-dependent RNA polymerase II, which is approximately 250 times less sensitive to inhibition by amanitin than the wild-type polymerase II whether tested in nuclei, in partially-fractionated extracts or as a highly purified enzyme. While the wild-type enzyme activity is inhibited 50% by 2.1 x 10(-8) M alpha-amanitin, inhibition of 50% of the AmaC4 RNA polymerase II activity requires a toxin concentration of 5.6 x 10(-6) M. The mutation responsible for the amanitin resistance of AmaC4 is on the X chromosome near the vermillion locus.

Amanitins↗
PubMed1979

Deletion mapping of two D. melanogaster loci that code for the 70,000 dalton heat-induced protein.

Using deficiencies in D. melanogaster that lack either the 87A or 87C heat-induced puffs, we have shown that the 70,000 dalton heat-induced protein (hsp 70) is encoded at both these loci. Embryos deleted for one of the two loci retain the ability to make hsp 70 after heat shock, but deleting both loci eliminates synthesis of hsp 70. Thus both loci encode hsp 70 and can be active following heat shock. We have analyzed the proteins made by embryos lacking either 87A or 87C, and have compared the 87A- and 87C-coded hsp 70 by isoelectric focusing and tryptic peptide fingerprinting. The hsp 70 made by the two loci is very similar, although a variant tryptic peptide appears to be encoded only at 87C. Using deficiencies with slightly different breakpoints, we have mapped the 87A locus to band 87A7, the site of the 87A heat-induced puff. The 87C locus maps within 87C1.

Animals↗
PubMed1979

Genetic and molecular analysis of the 87A7 and 87C1 heat-inducible loci of D. melanogaster.

Two different types of heat-inducible sequences are found at the cytogenetic loci 87A7 and 87C1 of D. melanogaster. One of these codes for the 70,000 dalton heat shock protein (hsp 70) and is found at both loci. The other type of sequence (alpha beta) codes for an RNA of unknown function and is found only at 87C1. We have completed a study of the organization of the two loci, using deficiencies that delete one or other locus, and have estimated the number of the hsp 70 genes at each locus. Thus in at least three strains of files there are a total of five coding sequences, three at 87C1 and two at 87A7. Restriction mapping of the coding regions at the two loci reveals that each of the two cytogenetic loci has its own characteristic coding sequence. The overall organization of the two loci appears to differ considerably. The alpha beta and hsp 70 heat-induced sequences at 87C1 are closely linked and are contained within two Eco RI restriction fragments.

Animals↗
PubMed1978

Two hybrid plasmids with D. melanogaster DNA sequences complementary to mRNA coding for the major heat shock protein.

The isolation and partial characterization of two cloned segments of Drosophila melanogaster DNA containing "heat shock" gene sequences is described. We have inserted sheared embryonic D. melanogaster DNA by the poly(dA-dt) connector method (Lobban and Kaiser, 1973) into the R1 restriction site of the ampicillin-resistant plasmid pSF2124 (So, Gill and Falkow, 1975). A collection of independent hybrid plasmids was screened by colony hybridization (Grunstein and Hogness, 1975) for sequences complementary to in vitro labeled polysomal poly(A)+ heat shock RNA. Two clones were identified which contain sequences complementary to a heat shock mRNA species that directs the in vitro synthesis of the 70,000 dalton heat-induced polypeptide. Both cloned segments hybridize in situ to the heat-induced puff sites located at 87A and 87C of the salivary gland polytene chromosomes.

Base Sequence↗
PubMed1979

Physical map of two D. melanogaster DNA segments containing sequences coding for the 70,000 dalton heat shock protein.

The isolation of the two hybrid plasmids 56H8 and 132E3, which contain D. melanogaster (Dm) DNA sequences complementary to the mRNA coding for the 70,000 dalton heat shock protein, has been reported (Schedl et al., 1978). Here we compare the sequence arrangement in the two cloned Dm DNA segments by restriction, cross-hybridization and heteroduplex analysis. The results show that the two cloned DNA segments derive from nonoverlapping regions of the Dm genome; that they contain homologous regions present once in 56H8 and twice in 132E3; and that each homologous region is composed of three distinct contiguous sequence elements, x, y and z, which together define a 3 kb common unit. While the 2.5 kb z elements show a high degree of sequence homology in all three common units, the three x and y elements display an intriguing relationship. The localization of the mRNA coding sequences within each of these common units is presented in the accompanying paper (Artavanis-Tsakonas et al., 1979).

Animals↗
PubMed1978

Genetic and molecular organization of the 5S locus and mutants in D. melanogaster.

The topography of an entire redundant locus was analyzed by both genetic and molecular means. Three mutants (min0, min1, min2) allelic to the 5S rRNA genetic locus on chromosome 2 of D. melanogaster were isolated. Flies exhibit a mutant phenotype when hemizygous for a min allele, but flies having two doses are wild-type. Saturation hybridization experiments show that the alleles are gross defieciencies each deleting an equal amount of 5S DNA. Each of the three mutant min alleles produces a distinct temperature-sensitive viability phene, and thus they are suggested to be pseudoalleles within the same redundant locus. Using the segmental aneuploid method (Lindsley et al., 1972), the 5S gene cluster was subdivided into proximal and distal halves. Both saturation hybridization experiments and genetic tests show that each half contains about eighty 5S genes. The complementation of the min alleles with the proximal and distal halves of the cluster indicates that both halves function independently. We present evidence which supports the model that all of the 160 5S genes are arranged as a single continuous cluster of tandem repeats with no large interdispersive DNA segments not complementary to 5S rRNA.

Alleles↗
PubMed1978

A novel arrangement of tandemly repeated genes at a major heat shock site in D. melanogaster.

Three cloned segments of Drosophila melanogaster DNA have been isolated that derive from the major heat shock site at 87C in chromosome 3. Each of these segments contains sequences homologous to a class of polysomal poly(A)+ RNAs whose synthesis is induced by heat shock of cultured cells. A combination of R loop, heteroduplex and restriction fragment maps of these segments reveals that their RNA-homologous sequences are arranged in tandemly repeated units, each unit consisting of an alpha element (0.49 kb) joined to a beta element (1.10 kb). The polysomal RNAs homologous to these alphabeta units (1.59 kb) are distributed into three size classes exhibiting approximate lengths of 1, 2 and 3 kb. R loop mapping demonstrated that the sequence of the 2 kb RNA is alphabetaalpha, indicating that it, and presumably the 3 kb RNA, derive from transcripts covering more than one repeated unit. One of the cloned segments contains a variant repeat unit, alphagamma, located between two alphabeta units. This unit has the same alpha element, but the beta element has been replaced by a nonhomologous gamma element (0.87 kb). Analysis of the total D. melanogaster DNA indicates that the 87C locus contains at least 21 tandemly repeated units, twelve of which were identified as alphabeta units and six as alphagamma units. The 21 or more units are distributed among at least three different tandem arrays separated by different spacer regions, one of which is within a cloned segment. Sequences in the gamma element, but not those in the alpha or beta elements, are also found at 87A, which contains another heat shock site. The possible roles of the alphabeta-type RNAs and of the gamma sequences are discussed in the light of these results.

Animals↗
PubMed1978

Drosophila hemolymph proteins: purification, characterization, and genetic mapping of larval serum protein 2 in D. melanogaster.

Three of the major protein species present in the hemolymph of Drosophila melanogaster larvae just prior to pupation are absent from second instar larvae but accumulate rapidly during the third instar. This article describes the purification and characterization of one of these, larval serum protein (LSP) 2, using an immunological assay. It is a homohexamer of molecular weight about 450,000, with a polypeptide molecular weight of 78,000--83,000. Fast and slow electrophoretic variants of this protein map between the markers vin and gs, at 36--37 on chromosome 3.

Animals↗
PubMed1979

Different behaviour of Xbb+ and Xbb chromosomes in D. melanogaster with only one nucleolus organizer.

We have examined the rDNA content of male and female adult flies having only one nucleolus organizer (NO), using X chromosomes carrying wild or partially deleted bobbed loci (Xbb+/O, Xbb+/XNO- and Xbb/O, Xbb/XNO-). The results show that in Xbb+/O and Xbb+/XNO- flies, where only somatic gene compensation is supposed to occur, the rDNA increase, althought less pronounced than previously reported, is directly proportional to the number of rRNA genes initially present in the nucleolus organizer. In Xbb/O and in Xbb/Xbb/XNO- flies the rDNA increase is relatively much higher than that observed in flies carrying bb+ instead of bb. It is suggested that this may be due to rDNA premagnification and somatic gene compensation occurring simultaneously in the former flies.

Animals↗
PubMed1979

Sequence organization of two recombinant plasmids containing genes for the major heat shock-induced protein of D. melanogaster.

We have isolated recombinant DNA clones which include cDNA and chromosomal DNA sequences of the major heat shock-inducible gene of Drosophila. With the cDNA fragments used as specific hybridization probes, DNA:DNA reassociation and in situ hybridization analysis demonstrated that the DNA sequences are repeated approximately 7 times in the haploid Drosophila genome, and that gene sequences are present at both the 87A and 87C loci on the cytological map. The cloned cDNA and homologous cloned chromosomal DNA hybridized to mRNA which translated in vitro into the major 70K heat shock-specific protein. Here we summarize a study of the organization of genes coding for the 70K heat shock-specific protein contained in the two recombinant chromosomal DNA plasmids pG3 and pG5. On the basis of R loop hybridization experiments and restriction enzyme analysis, we conclude that a 14 kb fragment, G3, contains three copies of the gene coding for the 70K protein. A second 9.2 kb fragment, G5, contains one copy of the gene coding for the 70K protein. Hybridization of labeled poly(A)-containing RNA to restriction endonuclease-cleaved DNA indicates that the mRNA coding regions in G3 and G5 are each approximately 2100 bp long. The three tandemly repeated genes of G3 are separated by approximately 1400 bp of spacer DNA. The two internal spacer regions in G3 appear to be identical, whereas differences in restriction enzyme sites indicate that the sequences adjacent to the cluster differ from the internal spacer and from each other.

Animals↗