Showing papers on "Gene published in 1970"
TL;DR: A new T7-specific RNA polymerase is found in T7 phage-infected cells and provides a direct explanation for the pleiotropic control of late T7 functions exerted by gene I.
Abstract: A new T7-specific RNA polymerase is found in T7 phage-infected cells It is the product of T7 gene I and is physically and biochemically distinct from the host cell RNA polymerase The synthesis of T7 RNA polymerase provides a direct explanation for the pleiotropic control of late T7 functions exerted by gene I
576 citations
TL;DR: It is found that for 29 species of cytochrome c the data fit the assumption that there is a group of approximately 32 invariant codons and that the remainder compose two Poisson-distributed groups of size 65 and 16 codons, the latter smaller group fixing mutations at about 3.2 times the rate of the larger.
Abstract: If one has the amino acid sequences of a set of homologous proteins as well as their phylogenetic relationships, one can easily determine the minimum number of mutations (nucleotide replacements) which must have been fixed in each codon since their common ancestor. It is found that for 29 species of cytochrome c the data fit the assumption that there is a group of approximately 32 invariant codons and that the remainder compose two Poisson-distributed groups of size 65 and 16 codons, the latter smaller group fixing mutations at about 3.2 times the rate of the larger. It is further found that the size of the invariant group increases as the range of species is narrowed. Extrapolation suggests that less than 10% of the codons in a given mammalian cytochrome c gene are capable of accepting a mutation. This is consistent with the view that at any one point in time only a very restricted number of positions can fix mutations but that as mutations are fixed the positions capable of accepting mutations also change so that examination of a wide range of species reveals a wide range of altered positions. We define this restricted group as the concomitantly variable codons. Given this restriction, the fixation rates for mutations in concomitantly variable codons in cytochrome c and fibrinopeptide A are not very different, a result which should be the case if most of these mutations are in fact selectively neutral as Kimura suggests.
465 citations
TL;DR: Seven mutants of E. coli with temperature-sensitive synthesis of DNA have been isolated and it has not yet proved possible to map accurately the mutants showing substantial residual synthesis, and the possibility that these mutations are in a different gene has not been excluded.
Abstract: Seven mutants of E. coli with temperature-sensitive synthesis of DNA have been isolated. Synthesis of RNA, protein and DNA precursors does not appear to be directly affected. The mutants can be divided into at least two groups on the basis of their pattern of DNA synthesis, their ability to support phage growth at 41° and their genetic mapping. Mutants of the first group are heterogeneous in their pattern of DNA synthesis at 40°. Some mutants cease DNA synthesis abruptly upon transfer to 40° and any residual DNA synthesis is barely detectable. In others there is substantial residual synthesis at 40°. All these Group 1 mutants are alike, however, in that they support the growth of phage T4 but not Lambda at 41°. Two mutants with barely detectable residual DNA synthesis carry DNA mutations which have been mapped by P1 transduction and show about 72% linkage to the malB locus. It has not yet proved possible to map accurately the mutants showing substantial residual synthesis, and the possibility that these mutations are in a different gene(s) has not been excluded. A single mutant has been placed in a second group. Like some Group 1 mutants it synthesizes substantial amounts of DNA at 40° before synthesis stops. However, unlike them it supports the growth of T4 and Lambda at 41°. The DNA mutation maps near the leu locus. Certain properties of this mutant are consistent with the idea that initiation of DNA synthesis is temperature-sensitive in this strain.
303 citations
TL;DR: By exploiting the natural ability of polyn nucleotides to align by base pairing and using polynucleotide kinase and ligase, chemically synthesized segments have been combined into double stranded DNA corresponding to the gene for the earliest characterized tRNA.
Abstract: By exploiting the natural ability of polynucleotides to align by base pairing and using polynucleotide kinase and ligase, chemically synthesized segments have been combined into a double stranded DNA corresponding to the gene for the earliest characterized tRNA.
248 citations
TL;DR: A method is described for isolating mutants of Saccharomyces cerevisiae which have lost repressibility by exogenous arginine for ornithine transcarbamylase and three complementary classes of mutations were found: argRI, argRII and argRIII which are recessive and define three loci.
Abstract: A method is described for isolating mutants of Saccharomyces cerevisiae which have lost repressibility by exogenous arginine for ornithine transcarbamylase.
Besides permeability mutants, three complementary classes of mutations were found: argRI, argRII and argRIII which are recessive and define three loci. No evidence for a linkage between any of these three loci or with the gene coding for ornithine transcarbamylase has been obtained.
Strains bearing mutations at either of these loci cannot be distinguished on a phenotype basis: after growth on minimal medium, the l-ornithine carbamoyl transferase activity is twice that of the wild type strain; the mutations modify neither the growth rate nor the permeability to arginine.
The mutations might affect the structure of an hetero-polypeptidic aporepressor.
The level of ornithine transcarbamylase in diploids is proportional to the number of argF+ genes in regulated as well as in non-regulated cells.
246 citations
TL;DR: The product of this gene cro prevents expression of immunity and regulates the expression of those genes to the left of the immunity region in bacteriophage λ.
Abstract: A new gene in bacteriophage λ is described. The product of this gene cro prevents expression of immunity and regulates the expression of those genes to the left of the immunity region. cro- mutants have been isolated and characterized.
222 citations
TL;DR: It is concluded that E. coli normally carries a pair of closely-linked genes specifying its minor, or suIII tyrosine tRNA, while the derivative carries a single suIII+ gene.
202 citations
TL;DR: Fifty temperature-sensitive mutants defective in DNA synthesis at high temperature have been identified among 655 temperature- sensitive mutants isolated at random from a mutagenised population of B. subtilis, suggesting that at least 14 genes are involved in B.subilis DNA replication.
Abstract: Fifty temperature-sensitive mutants defective in DNA synthesis at high temperature have been identified among 655 temperature-sensitive mutants isolated at random from a mutagenised population of B. subtilis. They are distributed in a non-random fashion in 9 genetic linkage groups, located in different regions of the B. subtilis genome. It is suggested that at least 14 genes are involved in B. subtilis DNA replication.
193 citations
TL;DR: The 5S RNA genes are placed within the region 56E-F of the right arm of chromosome 2 of Drosophila melanogaster, and their localization was determined from autoradiographs, where the radioactivity from hybrids of [3H]RNA and DNA was confined to the 56E -F segment.
Abstract: [ 3H ] RNA with a high specific activity was prepared from larvae of Drosophila melanogaster grown 4 days in contact with [ 3H ] uridine. Purified tritiated 5 S RNA was annealed to the DNA of polytene chromosomes, which had been denatured in formamide. The 5 S RNA genes are placed within the region 56E-F of the right arm of chromosome 2. This localization was determined from autoradiographs, where the radioactivity from hybrids of [ 3H ] RNA and DNA was confined to the 56E-F segment.
190 citations
TL;DR: Findings support a previously stated hypothesis that the genome of RNA tumor viruses is vertically transmitted as part of the natural genetic apparatus of normal mouse cells and suggest that the genes for RNA tumor virus, which later in life act as determinants of cancer, may be important also as gene determinants in the developing embryo.
Abstract: Tests for the group-specific antigen of the C-type RNA tumor virus showed that mouse embryos of all strains tested, at some stage of development in utero, revealed detectable titers of group-specific antigen in one or more of their tissues; younger, rather than older, embryos were likely to be positive, particularly in those strains which normally reveal little or no expression of the RNA genome postnatally. The antigens were found in embryos of low-leukemia strains, free of infectious virus. These new findings support a previously stated hypothesis that the genome of RNA tumor viruses, mostly switched off for infectious virus expression, is vertically transmitted as part of the natural genetic apparatus of normal mouse cells. Since group-specific antigens have also been described in chick embryos and immunological tolerance to homologous group-specific antigens has been demonstrated in hamsters and cats as well as in mice and chickens, the hypothesis has been extended to include vertebrate cells in general. Finally, the high incidence and titers of the group-specific antigen suggest that the genes for RNA tumor virus, which later in life act as determinants of cancer, may be important also as gene determinants in the developing embryo.
TL;DR: All of the temperature-sensitive mutants of Escherichia coli Kl2 carry mutations in the hsm gene, and it is argued that an hsm-directed polypeptide is required for restriction in addition topolypeptides directed by hssK and hsr.
TL;DR: RNA polymerase from sporulating cells of B. subtilis has a subunit structure different from the vegetative enzyme, which may be responsible for the turn-off of vegetative genes during spore formation.
Abstract: RNA polymerase from sporulating cells of B. subtilis has a subunit structure different from the vegetative enzyme. This alteration of RNA polymerase may be responsible for the turn-off of vegetative genes during spore formation.
TL;DR: Results are consistent with the idea that there is a site between genes Q and S that is necessary for expression of the late genes both in the right and in the left arms of the mature λ DNA molecule, at least in the prophage state.
TL;DR: It was concluded that few, if any, of the 5 s genes reside in the X or Y chromosomes, and therefore that most, if not all, ofThe genes for 5 s RNA are located in the autosomes.
TL;DR: Linkage between the major histocompatibility locus of inbred strain 2 guinea pigs and a "specific immune response gene," the PLL gene, which controls responsiveness to poly-L-lysine and hapten conjugates of this polypeptide in these animals is demonstrated.
Abstract: The data presented demonstrate linkage between the major histocompatibility locus of inbred strain 2 guinea pigs and a „specific immune response gene,” the PLL gene, which controls responsiveness to poly-L-lysine and hapten conjugates of this polypeptide in these animals. This finding extends to another species and to a different immune system the linkage observed in mice between the H2 locus and specific immune response genes at the Ir-1 locus. The general significance of the linkage of specific immune response genes to histocompatibility loci is discussed.
TL;DR: Amber mutants of phage T7 defective in gene 3 are unable to produce the enzyme after infection of the nonpermissive host, and mutants that produce a heat-labile endonuclease were found, indicating that this gene is the structural gene for the enzyme.
Abstract: Infection of Escherichia coli with bacteriophage T7 results in the appearance of an endonuclease activity capable of hydrolyzing both double-and single-stranded DNA. Treatment with chloramphenicol prevents the induction of the endonuclease. Amber mutants of phage T7 defective in gene 3 are unable to produce the enzyme after infection of the nonpermissive host, and mutants that produce a heat-labile endonuclease were found, indicating that this gene is the structural gene for the enzyme. Gene 3 mutants synthesize only a limited amount of DNA. In addition, they are defective in carrying out the degradation of host DNA, suggesting that the gene 3 endonuclease is involved in this function.
TL;DR: It is concluded that the gene A protein is required for DNA replication and expression of other essential genes, and that it work only on the chromosome from which it was formed, i.e., it works only in cis.
TL;DR: Resistance loci for a number of antibiotics known to inhibit protein synthesis have been mapped on the Bacillus subtilis W168 genome by transformation, PBS1 transduction and density transfer analysis.
TL;DR: The degradation of bacterial deoxyribonucleic acid (DNA) was studied after infection of Escherichia coli B with DNA-negative amber mutants of bacteriophage T7 to find out whether the DNA was reduced to acid-soluble products or cleaved endonucleolytically.
Abstract: The degradation of bacterial deoxyribonucleic acid (DNA) was studied after infection of Escherichia coli B with DNA-negative amber mutants of bacteriophage T7. Degradation occurred in three stages. (i) Release of the DNA from a rapidly sedimenting cellular structure occurred between 5 and 6 min after infection. (ii) The DNA was cleaved endonucleolytically to fragments having a molecular weight of about 2 × 10 6 between 6 and 10 min after infection. (iii) These fragments of DNA were reduced to acid-soluble products between 7.5 and 15 min after infection. Stage 1 did not occur in the absence of the gene 1 product (ribonucleic acid polymerase sigma factor), stage 2 did not occur in the absence of the gene 3 product (phage T7-induced endonuclease), and stage 3 did not occur in the absence of the gene 6 product.
TL;DR: An effect of mutation conferring loss of one enzyme of the cycle on the specific activity of the other enzymes in the cycle was observed.
Abstract: The genetic location of mutations affecting the citric acid cycle and the properties of mutants of Bacillus subtilis possessing these mutations have been examined. Genes coding for the component enzymes of the cycle were found to be unlinked to each other and thus do not form an operon. The mutational defect in a mutant lacking fumarase mapped between thr-5 and cysB3. Mutations causing inability to produce isocitrate dehydrogenase and succinate dehydrogenase were found to map between argA11 and leu-1. The alpha-ketoglutarate dehydrogenase mutations were mapped at the terminal end of the B. subtilis chromosome through a weak linkage in phage PBS-1 transduction of one class of these mutations of ilvA2 and metB4. A second class of alpha-ketoglutarate dehydrogenase mutations mapped closer to ilvA2 and metB4 but still terminal with respect to these markers. Aconitaseless mutants possessed mutations that could not be linked to any of the known transducing segments of the chromosome. An effect of mutation conferring loss of one enzyme of the cycle on the specific activity of the other enzymes in the cycle was observed.
TL;DR: Specific regions of the phage particle were found to be associated with antibodies when they were reacted with such absorbed antisera and the implications for phage T4 assembly are discussed.
TL;DR: The hypothesis is developed that secondary amber mutations similarly lower the level of a second component involved in phage assembly, indicating a balance of assembly processes that is essential for normal phage morphogenesis is restored.
TL;DR: Gene dosage and dominance effects observed in merodiploid strains indicate that the glyT and glyU genes are the structural genes for the affected glycine tRNA species, and each of the species is completely altered by single mutations, showing that there is only one structural gene per genome for each of these species.
TL;DR: During the germination of wheat embryos, modifications occur in the resting DNA, and about 30 per cent of the ribosomal genes—both 24S and 17S—are missing in the genome of germinated embryos.
Abstract: During the germination of wheat embryos, modifications occur in the resting DNA. About 30 per cent of the ribosomal genes—both 24S and 17S—are missing in the genome of germinated embryos.
TL;DR: If one considers investigations of random products of meiosis, one class of observations is characterized by unidirectional regular exchange for the closely linked flanking markers which permits the construction of a unique, and internally consistent, linear map of sites within the complex.
Abstract: TUDIES of recombination in Drosophila involving closely linked markers (i.e., separable sites within a complex locus) have yielded results which may be grouped into at least two classes. Thus, if one considers investigations of random products of meiosis, one class of observations is characterized by: (1 ) unidirectional regular exchange for the closely linked flanking markers which permits the construction of a unique, and internally consistent, linear map of sites within the complex. (2) Positive interference is seen in that all products of exchange between the marker sites within the complex are classifiable as products of single-exchange tetrads. An example of such data are those seen in the study of the lozenge complex (GREEN and GREEN 1949,1956). In contrast, the garnet mutants (CHOVNICK 1958, 1961), maroon-like mutants (FINNERTY, DUCK and CHOVNICK 1970) and Notch mutants (WELSHONS and VON HALLE 1962; BAILLIE, ASTELL and SCHOLEFIELD 1966) yield meiotic products which appear to reflect negative interference in conjunction with exchange between the mutants within the complex. Nevertheless, if one restricts attention to the apparent singleexchange products in these systems, unambiguous linear mapping of sites within the complex obtains. Although full tetrad analysis is not possible in Drosophila, investigation of the reciprocity of recombination events at complex loci is afforded by use of compound chromosomes such as the attached-X chromosome and compound autosomes, which permit recovery of half-tetrad products of meiosis. Recombination studies with such chromosomes in Drosophila provide complete confirmation of the classical principles of exchange for relatively distant chromosome markers (WELSHONS 1955; BALDWIN and CHOVNICK 1967). However, studies of the halftetrad products of exchange involving very closely linked markers, like the random strand analyses, may be divided into two categories of results. One class of observations on exchange events between mutant members of a gene complex is best exemplified by the bithorax system of mutants (LEWIS 1967). In this system, exchanges are reciprocal, and positive interference appears to be the rule. On
TL;DR: The results confirm the view that only part of the viral genome is under direct immunity control and suggest that some transcription is initiated in the presence of the N -gene product at a site located in the y-cII region.
TL;DR: The virus-specific RNA synthesized 18 hours after infection was not found in transformed cells, suggesting that either these late viral genes are not present or are not transcribed in adenovirus type 2 transformed cells.
Abstract: DNA-RNA hybridization-competition experiments were used to compare the virus-specific RNA sequences synthesized during productive infection with human adenovirus type 2 with those synthesized in virus-free adenovirus type 2 transformed cells. The „early” virus-specific RNA present at six hours after infection, prior to the onset of viral DNA synthesis, represents 8-20 percent (2 to 10 genes) of the viral genome. All viral RNA sequences synthesized early are also present „late,” at 18 hours after infection. The base sequences transcribed in transformed cells are homologous to approximately 50 per cent of the sequences transcribed early after infection. Thus only 4 to 10 per cent of the viral genome, representing 1 to 5 viral genes, are transcribed in adenovirus type 2 transformed cells. The virus-specific RNA synthesized 18 hours after infection was not found in transformed cells, suggesting that either these late viral genes are not present or are not transcribed in adenovirus type 2 transformed cells.