Showing papers on "Genome published in 1970"
TL;DR: A new method is described for the determination of the total molecular weight of haploid genome DNA based on initial optical renaturation rate measurements of precisely known concentrations of fragmented DNA that appears to offer advantages by its simplicity, rapidity and reproducibility.
Abstract: A new method is described for the determination of the total molecular weight of haploid genome DNA. It is based on initial optical renaturation rate measurements of precisely known concentrations of fragmented DNA. The theoretical basis of the measurement is presented. The actual state of replication of the genome has little effect. The exact conditions and the effects of DNA concentration, renaturation time, size of DNA fragments, buffer concentration, optimal temperature and % (G + C) have been determined. Several types of bacterial DNA of known genome size were included as a control. As an application, the DNA genome size have been determined of 40 different bacteria. The method appears to offer advantages by its simplicity, rapidity and reproducibility.
426 citations
TL;DR: Unless very small selective pressures are effective, it seems that no mechanisms exist to establish optimum mutation rates in sexual organisms.
Abstract: In sexual organisms, alleles increasing the mutation rate of the entire genome are invariably selected against, whereas in asexual organisms such "general mutators" are favored if they adjust the mutation rate closer to an optimum balancing the advantages of responsiveness to environmental change against those of a small mutational load. Unless very small selective pressures are effective, it seems that no mechanisms exist to establish optimum mutation rates in sexual organisms.
223 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
183 citations
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.
101 citations
TL;DR: A phage lambda gene, called tof, responsible for the turnoff of λ-exonuclease synthesis during the lytic cycle has been located in the region of the lambda genome which is nonhomologous with the λi 434 genome.
94 citations
TL;DR: Studies from several laboratories show that mammalian and bacterial viruses may induce changes in the translational mechanism of their host cells, and changes were observed in the tRNA, in the enzymes modifying the t RNA (such as tRNA methylases and tRNA thiolases), or in the aminoacyl-tRNA synthetases.
Abstract: The events taking place after a viral nucleic acid enters a susceptible host cell depend on the specific viral system. In the case of the DNA-containing viruses (1), the nucleic acid serves as a template both for its own replication and for the transcription of viral specific mRNA which is then translated into viral proteins. It has been generally thought that the various components of the host translational system remain unaltered and are utilized for the synthesis of viral proteins; the viral mRNA becomes attached to the preexisting host cell ribosomes, and viral polypeptides are then synthesized by the preexisting host cell tRNA and aminoacyl-tRNA synthetases. This is a rather simplified presentation of the events taking place during synthesis of viral proteins. Recent experiments show that the picture may be more complicated, and, at least in the case of some viruses, a more intricate translational mechanism is involved. Studies from several laboratories show that mammalian and bacterial viruses may induce changes in the translational mechanism of their host cells. These changes were observed in the tRNA, in the enzymes modifying the tRNA (such as tRNA methylases and tRNA thiolases), or in the aminoacyl-tRNA synthetases. The evidence for changes in the translation mechanism which follow virus infection is summarized below. Several modifications of tRNA induced by virus infection have been observed. Thus, the chromatographic profile of leucine tRNA in Escherichia coli is altered after the bacterial cells have been infected with T2 bacterio-
78 citations
70 citations
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.
62 citations
TL;DR: Electrophoretic work further elucidated or confirmed taxonomic relations between species obtained previously by well known classical methods of geographical, morphological, cytological, and hybridization analyses.
Abstract: Polyacrylamide gel electrophoresisof seed proteins offers a biochemical approach to the evolutionary aspects of plant speciation. The background and theory of polyacrylamide gel electrophoresis were thoroughly discussed by Ornstein (1964), and the method and application of the technique to analyze and compare human serum proteins were presented by Davis (1964). Amino acid changes within a protein, due to mutational changes, can result in altered protein migration rates when the proteins are compared in the matrix system of polyacrylamide. Therefore, since species differ genetically at many loci, the individuality of each plant species can usually be expressed according to its protein banding pattern. Steward et al. (1965), Boulter et al. (1966), and Sastry and Virupaksha (1967) modified the polyacrylamide gel electrophoretic technique so as to detect protein changes in developing and differentiating plant seedlings and to examine protein content of seeds. Many workers believe proteins from seed or other dormant tissue from plants represent a more stable reflection of the genomic state in a given species than that obtained from developing seedlings. Subsequently, their electrophoretic work further elucidated or confirmed taxonomic relations between species obtained previously by well known classical methods of geographical, morphological, cytological, and hybridization analyses. For example, Fox et al. (1964) with Leguminoseae, Vaughan
62 citations
TL;DR: A two-unit interaction is suggestive of a form of gene control that was proposed by JACOB & MONOD (196 1) for the bacterial lac operon; an element at the locus is triggered by a second element before gene activity can occur.
Abstract: A significant feature of mutable loci in maize (RHOA~ES, 1941; MCCLINTOCK, 1951, 1965; PETERSON, 1965a) is the interaction of genetic elements that control gene action. “Controlling elements” recognizable only at the locus they control, by affecting an “off” state of the gene, respond to “regulatory elements” and, thus, phenotypic changes are initiated. This two-unit interaction is suggestive of a form of gene control that was proposed by JACOB & MONOD (196 1) for the bacterial lac operon; an element at the locus is triggered by a second element before gene activity can occur. Similarity between maize and bacterial systems was noted by MCCLINTOCK (1961) who compared numerous specific cases. What is evident in most systems that have been described in maize is that locus activity is suppressed by the presence of an identifiable element, the controlling element *s) such as I and Ds or unnamed elements of specific alleles such as al m-i. Like its bacterial counterpart, it resides close to the locus and is operative only in the cis * position. Further, this element has a high degree of specificity, manifest in the singular distinctiveness of its response to a particular regulatory element such as En or AC only. (The elements of such an interaction compose a system). In maize, several systems have been described (listed as controlling-regulatory elements) aldt-Dt (RHOADES, 1936, 1938, 1941; NUFFER, 1961), Ds-AC (MCCLINTOCK, 1951, 196.5),
TL;DR: The present work has posed the question whether the reovirus genome is a continuous, double-stranded molecule or whether there are discontinuities in the complementary strands of RNA that might constitute "weak points" in the structure and developed a method to estimate the 3'-terminal nucleosides of RNA within intact virions.
Abstract: The double-stranded RNA genome of reovirus breaks reproducibly into ten segments upon extraction from purified virions. Reovirus-induced messenger RNA's formed in infected cells correspond in length to these ten genomic segments and some real structural and biological implication must be accorded to the ready manner in which the genome is fragmented on attempted isolation. In the present work we have posed the question whether the reovirus genome is a continuous, double-stranded molecule or whether there are discontinuities in the complementary strands of RNA that might constitute „weak points” in the structure. To answer this question, a method was developed to estimate the 3′-terminal nucleosides of RNA within intact virions. Approximately as many 3′-ends are free inside the virion as in RNA extracted from purified virus. Thus, the viral genome exists as a discontinuous structure inside the virus particle and both strands of the duplex are interrupted at intervals.
TL;DR: It has been shown that hybrid cells which have lost T-antigen are capable of synthesizing this antigen upon infection with SV40, thereby demonstrating that loss of the viral antigen from the hybrid cells is not due to loss of some cellular gene required for the expression of theiral genome.
Abstract: The study of hybrids from three crosses between mouse cells and SV40-transformed human cells have established a positive correlation between the loss of human chromosomes and that of the SV40-induced T-antigen from the hybrid cells. These results, as well as those of other workers, provide strong support for the hypothesis of the integration of the SV40 genome in the chromosomes of transformed cells. Further, it has been shown that hybrid cells which have lost T-antigen are capable of synthesizing this antigen upon infection with SV40, thereby demonstrating that loss of the viral antigen from the hybrid cells is not due to loss of some cellular gene required for the expression of the viral genome. Results of karyological analyses of the hybrid cells argue against the existence of a single specific integration site for the SV40 genome in human cells.
TL;DR: It has been suggested that parasitic organisms have a simpler genome than their free-living counterparts, and the rate of renaturation of the slowest reacting components can be used to measure the "kinetic complexity" of an organism.
Abstract: It has been suggested that parasitic organisms have a simpler genome than their free-living counterparts. Measurements by reciprocal DNA hybridizations in vitro have shown that the parasitic plant Cuscuta californica has a smaller genome than several closely related autotrophic plants (Searcy, 1970). These studies have the shortcoming of detecting only the hybridization of the highly repetitive sequences of DNA; the non-repetitive sequences react too slowly to hybridize significantly under the conditions used (Melli and Bishop, 1969; Britten and Kohne, 1968). The size of the genome may also be determined by DNA renaturation. Denatured DNA fragments can be made to renature in vitro, forming a specifically base-paired structure as in native DNA (Marmur and Doty, 1961). As predicted theoretically, and as confirmed empirically, the rate of renaturation is inversely related to the molecular weight of the entire DNA molecule of phages and bacteria (Marmur and Doty, 1961; Bolton et al., 1965; Britten and Kohne, 1968; Wetmur and Davidson, 1968). The DNA of higher organisms renatures faster than would be predicted from the haploid complement of DNA because of the presence of highly repetitive DNA sequences (Waring and Britten, 1966; Britten and Kohne, 1968). However, the rate of renaturation of the slowest reacting components can be used to measure the "kinetic complexity" of an organism, which is a measure of the total number of different sequences in the DNA of an organism (Wetmur and Davidson, 1968).
Journal Article•
TL;DR: The transfer of deoxyribonucleic acid (DNA) from bacteriophage SP82G to its host may be halted by chilling but is affected little by chloramphenicol, actinomycin D, or cyanide.
Abstract: The transfer of deoxyribonucleic acid (DNA) from bacteriophage SP82G to its host may be halted by chilling but is affected little by chloramphenicol, actinomycin D, or cyanide. The order of entry of markers on the phage genome was determined by halting the transfer of DNA at intervals, removing the untransferred DNA by blending, and assaying for the presence of markers in the blended complexes. Markers on the phage genome are transferred in a linear, polar fashion consistent with the previously determined genetic and physical maps. Those markers concerned with early functions enter first, and the rate of transfer is temperature dependent.
TL;DR: Cell association and cell fusion of a number of simian virus 40-transformed cell lines with sensitive green monkey cells resulted in SV40 rescue, and this finding is significant particularly for the study of poorly infectious oncogenic viruses because it represents a new experimental approach to their detection.
Abstract: Publisher Summary This chapter reviews the data showing the ways virus–cell interaction is modified if different cellular mixtures are employed. It considers the situations in which cell-to-cell contact between virus-producing cells and uninfected resistant cells allows the penetration of a virus into uninfected cells. Cell association is an important factor in effecting both the spread of virus infection and infection of resistant cells. Convincing evidence has been obtained so far with herpes viruses and myxoviruses—that is, viruses that initiate cell fusion. Experimentally induced cell fusion permits the penetration of pathogenic and oncogenic viruses into resistant cells where they also replicate. This finding is significant particularly for the study of poorly infectious oncogenic viruses because it represents a new experimental approach to their detection. Cell association played an important role in the experiments on virus rescue from tumor cells transformed by oncogenic viruses that do not produce infectious virus, although there is some indirect experimental evidence showing that the viral genome is present in the transformed cells. This evidence is mainly based on the finding of virus-specific antigens and nucleic acids. Cell association and cell fusion of a number of simian virus 40 (SV40)-transformed cell lines with sensitive green monkey cells resulted in SV40 rescue.
TL;DR: The DNA cistrons that code for tRNA in Escherichia coli have been isolated by repeated hybridization of DNA with tRNA and fractionation of DNA–RNA hybrids and non-tRNA cistsrons by chromatography on hydroxyapatite columns.
Abstract: The DNA cistrons that code for tRNA in Escherichia coli have been isolated by repeated hybridization of DNA with tRNA and fractionation of DNA–RNA hybrids and non-tRNA cistrons by chromatography on hydroxyapatite columns. The tRNA cistrons comprise 0.04–0.06 per cent of the E. coli genome and may be located contiguously on the chromosome.
TL;DR: Synthetic triploid hybrids of Elymus innovatus apparently contains a genome closely homologous with the E. junceus genome, and the genomes of the octoploid E. cinereus and four tetraploid species may be represented by the basic genome formula JJXX.
Abstract: A B S T R A C T Synthetic triploid hybrids of Elymus junceus Fisch. (2n = 14) X E. innovatus Beal (2n = 28) averaged 7.05', 6.73II, and 0.16III in 92 metaphase-I cells. The hybrids were totally sterile. Elymus innovatus apparently contains a genome closely homologous with the E. junceus genome. Natural tetraploid hybrids of E. innovatus X E. dasystachys Trin., E. dasystachys X E. triticoides Buckl., and E. triticoides X E. cinereus Scribn. & Merr. generally formed 14 bivalents at metaphase I; and subsequent meiotic stages were correspondingly regular. Nevertheless, none of the hybrids set seed. The four tetraploid species may be represented by the basic genome formula JJXX, where J is an E. junceus-like genome; and X is a genome of undetermined origin. The E. junceus genome likely exists in other long-anthered cross-pollinating Elymus species. Genome relations were difficult to interpret in a natural 42-chromosome hybrid of E. dasystachys X octoploid E. cinereus, which averaged 8.51I. 13.82",1 1.85III, and 0.08Iv in 39 metaphase-I cells. Although octoploid E. cinereus likely arose from the tetraploid form, the genomes of the octoploid have become somewhat restructured.
TL;DR: Synthesis of these two proteins is controlled by the homeologous chromosomes 7B and 7D respectively, but Aegilops speltoides, the more generally accepted B genome donor, does not synthesize the 7B protein.
Journal Article•
TL;DR: The initial uptake rats of several exogenous substrates was measured in a series of isogenic strains of yeast including haploid, diploid, triploid and tetraploid organisms, finding that the relative uptake rate decreases in the same proportions as the ratio surface to volume.
TL;DR: A general method is developed which enables to study the transcription of individual genes of phage T4 (Jayaraman and Goldberg, 1969) and cannot distinguish individual messenger RNAs (mRNAs) synthesized in vivo or in vitro.
Abstract: Transcription of bacteriophage T4 genome has been studied extensively in vivo (Bolle et al., 1968a, 1968b; Salser et al., 1970) and in vitro (Travers, 1970). These studies utilized RNA-DNA hybridization and hybridization competition techniques to characterize various classes of RNA. Such techniques are useful in distinguishing between classes of RNA, for example, early and late phage RNA, but cannot distinguish individual messenger RNAs (mRNAs) synthesized in vivo or in vitro. We have recently developed a general method which enables us to study the transcription of individual genes of phage T4 (Jayaraman and Goldberg, 1969).
Journal Article•
TL;DR: Chromosome pairing in the F1 hybrid between the cultivated oat Avena sativa and A. ventricosa, and in the derived amphiploid, shows that the diploid species is related to one of t...
Abstract: Chromosome pairing in the F1 hybrid between the cultivated oat Avena sativa and a diploid species A. ventricosa, and in the derived amphiploid, shows that the diploid species is related to one of t...
TL;DR: The amphidiploids exhibited a DNA content intermediate between that of the A and D genomes, and there was, however, no distinct correlation between RNA content and species or genome grouping.
TL;DR: Cytological analysis of eight interspecific hybrids of Phalaenopsis, (2n=38), intra-as well as intersectional, involving eight species, revealed various degrees of genome homology.
Abstract: Cytological analysis of eight interspecific hybrids ofPhalaenopsis, (2n=38), intra-as well as intersectional, involving eight species, revealed various degrees of genome homology. The species can be divided into two groups. Within each of the groups a strong genome homology occurs. The first group comprises the speciesP. amabilis, P. stuartiana, P. sanderiana, P. aphrodite andP. equestris, all having similar genomes of small chromosomes. The second group includesP. lueddemanniana, P. mannii andP. amboinensis, having genomes comprising larger chromosomes. In addition, the genomes of the latter three species have a different average chromosome size. Cytological evidence for differences in length at somatic metaphase as well as in metaphase I configurations in hybrids of species of the second group is presented. Hybrids between representative species of the first and the second group show poor to fair genome homology. The implications of the cytological observations for the classification ofPhalaenopsis are discussed.