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At least 1,423 records · Page 79Linked to original sources
PubMed1976

Construction of a hybrid col E1 plasmid carrying the gene for bacteriophage lambda repressor.

A biologically active hybrid DNA molecule was constructed from plasmid Col E1 and the Eco R1 fragment of lambda DNA containing the gene for lambda repressor. The presence of this gene in the hybrid molecule was demonstrated genetically. The hybrid plasmid contains two closely located targets for restriction endonuclease Hind 111 in the integrated fragment. Thus, the plasmid may be used as a vector not only for Eco R1 fragments but also for Hind 111 fragments.

Colicins↗
PubMed1976

On the isolation of TI-plasmid from Agrobacterium tumefaciens.

An efficient lysis method for Agrobacterium cells was developed, which allows a reproducible isolation of the tumor inducing (TI)-plasmid. The lysis method is based on the sensitivity of this bacterium to incubation with lysozyme, n-dodecylamine,EDTA, followed by Sarkosyl, after growth in the presence of carbenicillin. We also present a procedure for the isolation of the TI-plasmid on a large scale, that might be used for the mass isolation of other large plasmids which like the TI-plasmid, can not be cleared with earlier described procedures. The purity of the plasmid preparations was determined with DNA renaturation kinetics, which method has the advantage that the plasmid need not to be in the supercoiled or open circular form.

Centrifugation, Density Gradient↗
PubMed1977

Studies of ColE1-plasmid DNA and its interactions with histones: sedimentation velocity studies of monodisperse complexes reconstituted with calf-thymus histones.

Complexes between the four calf-thymus histones (H2A, H2B, H3 and H4) and colE1-plasmid DNA have been reconstituted using the procedure of Oudet et al. ((1975), Cell 4, 281-300). The sedimentation rates of the complexes formed were studied under a variety of conditions. In 0.4 MNaCL, 0.1 M Tris pH 7.50, 0.01 M EDTA and 0.02 M NaHSO3, the final dialy-sis-solvent in the reconstitution procedure, the sedimentation coefficients s23 were found to increase when the complexes were reconstituted at increasing histone to DNA ratios. True plateau regions were reached in the case of the relaxed circular and linear forms of the plasmid DNA. The sedimenting boundaries observed for the complexes at saturation are sharp, reflecting a narrow distribution of sedimentation coefficients and a homogeneity of the complex comparable to that of the uncomplexed DNA. Studies of the dependence of s 23 on the concentration of the complex at constant DNA to histones ratio have been undertaken at salt concentrations between 0.4 and 1.5 M NaCL in the above solvent. The formation of the complexes is reversible, at least at the higher ionic strengths. At salt concentrations below 0.36 M the complex precipitates from solution. Omission of histone H4 from the reconstitution mixture abolishes complex formation.

Animals↗
PubMed1977

Analysis of chromosomal integration and deletions of yeast plasmids.

Plasmid DNAs from six strains of Saccharomyces cerevisiae were compared. Three different plasmids were found, designated Scp 1, Scp 2 and Scp 3, with monomer lengths of 6.19, 6.06 and 5.97 kilobases as referenced to sequenced phiX174 DNA. DNA from each of the plasmids was inserted into a lambda vector DNA. Hybrid phage containing inserted DNA of the desired size were enriched by genetic selection and their DNAs analysed by rapid techniques. All three plasmids share the same organization, two unique sequences separated by two inverted repeats, and share basically the same DNA sequences. Scp 2 and Scp 3 differ from Scp 1 by missing a unique HpaI site and by having small overlapping deletions in the same region. The HpaI site in Scp 1 is, therefore, in a nonessential region and suitable for insertion of foreign DNA in the potential use of the yeast plasmid as a vector. Hybridization of labelled cloned plasmid DNA to restriction fragments of linear yeast DNA separated on agarose gels showed that the plasmid DNA was not stably integrated into the yeast chromosomal DNA.

Chromosomes↗
PubMed1977

Physical properties and gel electrophoresis behavior of R12-derived plasmid DNAs.

A series of closed circular (I) plasmid DNAs has been derived from drug resistance factor R12, and the nicked circular (II) and linear (III) derivatives of these molecules prepared by irradiation in the presence of ethidium bromide and by treatment with restriction enzyme EcoRI, respectively. These DNAs encompass the molecular weight range 3.6 to 61 megadaltons. The base compositions range from 45% to 51% (GC) as estimated by buoyant density determinations. The smaller plasmids are significantly less supercoiled (9-10%) than are the larger (12-13%). The gel electrophoretic behavior of the three DNA structural forms was determined as a function of molecular weight in agarose gels of concentrations ranging from 0.7% to 1.6% and at electrophoresis salt concentrations from 0.02 M to 0.08 M sodium acetate. The mobilities of DNAs I and III undergo a reversal relative to each other at a molecular weight which decreases with increasing agarose gel concentration. The molecular weight at which DNA II fails to enter a gel depends upon the ionic strength during electrophoresis but not upon the gel concentration.

Centrifugation, Density Gradient↗
PubMed1975

Mode of replication of plasmid lambda-dv-1.

About 20 copies of plasmid lambda-dv are perpetuated per host chromosome in Escherichia coli K12 cells. The mode of DNA replication of this plasmid lambda-dv was studied, using the density-labelling technique followed by banding in DsCl. It was shown that all the copies of plasmid lambda-dv are potentially capable of replicating roughly once a cell generation. Their replication occurs by random, that is a copy of the plasmid is taken out at random for replication from a pool, to which the two replicas resulting from replication are returned. Chloramphenicol did not inhibit the initiation of a new round of replication of the plasmid molecules, indicating that selection from the replication pool does not require concomitant protein synthesis.

Cell Division↗
PubMedDate not supplied

A genetic maternal effect on egg surface in Tribolium castaneum.

Females homozygous for an autosomal recessive gene, wd, produce "weird" eggs that are dry when laid. The wd gene has some important population consequences and also provides a very useful example of a genetic maternal effect for laboratory courses.

Animals↗
PubMedDate not supplied

Sterility in D. melanogaster due to nucleocytoplasmic interactions.

A case of sterility in Drosophila melanogaster is due to the interaction between a second chromosome recessive conditional gene, str(2)350, recovered from a natural population and the cytoplasm. The gene is located between Sp(22.0) and B1(54.8) about one-eighth the distance from B1. The final effect of this interacting system is the suppression of gonad development in both sexes.

Animals↗
PubMed1998

Association between chloroplast and mitochondrial lineages in oaks.

Patterns of chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation were studied in 378 populations of oak trees sampled throughout the southern half of France. Six cpDNA haplotypes detected in a previous European survey and three new cpDNA haplotypes were found in this region. Two mitochondrial polymorphisms detected earlier by restriction analysis of PCR-amplified fragments alone, or in combination with single-strand conformation polymorphism (SSCP), were compared with the cpDNA data. Sequencing revealed the nature of the two mitochondrial mutations: a single-base substitution and a 4-bp inversion associated with a 22-bp hairpin secondary structure. The single-base substitution was then analyzed by allele-specific amplification. Results for the two cytoplasmic genomes were combined, which allowed the identification of 12 cpDNA-mtDNA haplotypes. The 4-bp mtDNA inversion has appeared independently in different cpDNA lineages. Given the peculiar nature of this mtDNA mutation, we suggest that intramolecular recombination leading to repeated inversions of the 4-bp sequence (rather than paternal leakage of one of the two genomes) is responsible for this pattern. Furthermore, the geographic locations of the unusual cpDNA-mtDNA associations (due to the inversion) usually do not match the zones of contact between divergent haplotypes. In addition, in southern France, the groupings of populations based on the mtDNA substitution were strictly congruent with those based on cpDNA. Because many populations that are polymorphic for both cpDNA and mtDNA have remained in contact since postglacial recolonization in this area without producing any new combination of cytoplasms involving the mitochondrial substitution, we conclude that paternal leakage is not a significant factor at this timescale. Such results confirm and expand our earlier conclusions based on controlled crosses.

Base Sequence↗
PubMed1991

Mitochondrial DNA in the sea urchin Arbacia lixula: evolutionary inferences from nucleotide sequence analysis.

From the stirodont Arbacia lixula we determined the sequence of 5,127 nucleotides of mitochondrial DNA (mtDNA) encompassing 18 tRNAs, two complete coding genes, parts of three other coding genes, and part of the 12S ribosomal RNA (rRNA). The sequence confirms that the organization of mtDNA is conserved within echinoids. Furthermore, it underlines the following peculiar features of sea urchin mtDNA: the clustering of tRNAs, the short noncoding regulatory sequence, and the separation by the ND1 and ND2 genes of the two rRNA genes. Comparison with the orthologous sequences from the camarodont species Paracentrotus lividus and Strongylocentrotus purpuratus revealed that (1) echinoids have an extra piece on the amino terminus of the ND5 gene that is probably the remnant of an old leucine tRNA gene; (2) third-position codon nucleotide usage has diverged between A. lixula and the camarodont species to a significant extent, implying different directional mutational pressures; and (3) the stirodont-camarodont divergence occurred twice as long ago as did the P. lividus-S. purpuratus divergence.

Amino Acid Sequence↗
PubMed1991

Evidence for replication slippage in the evolution of Oenothera chloroplast DNA.

Evolutionary relationships of four plastid genomes (plastomes) from different Oenothera species have been assessed by sequence comparisons of two intergenic regions that separate the ribosomal protein genes rpl16, rpl14, and rps8. Sequence changes include base substitutions, the occurrence of a 29-base tandem duplication, and variation in the length of two poly-A stretches. Additions/deletions in chloroplast DNA may not be useful for evolutionary comparisons more distant than these, particularly if the sequences undergo divergence after the initial event, but the length mutations reported here allow a finer resolution of the phylogeny of the closely related Oenothera plastomes than would have been possible if only base substitutions had been considered. Comparisons with the orthogous sequence from tobacco chloroplast DNA indicate the direction of change at most of the sites. The results suggest that plastomes I and II are closely related to each other, as are plastomes III and IV. Replication slippage is proposed as a mechanism to explain the length mutations.

Base Composition↗
PubMed1992

Sequence instability and functional inactivation of murine Y chromosomes can occur on a specific genetic background.

When the Y chromosome from Mus. poschiavinus (YPos) is backcrossed onto the C57BL/6J laboratory strain, testicular dysfunction occurs at high frequencies. When five different multicopy probes from the recombinationally suppressed region of the Y chromosome were used, genomic DNAs from sibling female progeny of C57BL/6J YPos males were found to contain YPos-specific sequences ranging from trace levels to levels consistent with an intact Y chromosome. Females with a high copy number of YPos-specific sequences had a karyotype of XYPos and were sterile. Females with trace levels of these sequences were XX and fertile. Repeated sequences in the testis-determining-region (Sxr) of inactive YPos chromosomes were unstable relative to sequences in non-Sxr regions. In contrast, the YPos chromosome was stable and functioned normally in other inbred laboratory strains such as 129/Sv. The frequency and extent of YPos chromosome instability increased with successive backcrosses from stable (129/Sv) to unstable (C57BL/6J) genetic backgrounds. Traces of YPos-specific sequences were first detected in N2 female offspring of F1 males. Therefore, sequences were deleted from YPos chromosomes in the F1 male germ line and were transmitted to N2 females; inactive YPos chromosomes (XYPos females) were first detected in the N3 generation. The mouse line being derived by backcrossing the YPos chromosome onto C57BL/6J inbred strains ended in the N7 generation, since all XYPos offspring were sterile. Even stable repeated sequences from the non-Sxr regions of their inactive YPos chromosomes were precisely rearranged in these N7 offspring at high frequencies. These data are consistent with hybrid dysgenesis in mammals.

Animals↗