Showing papers on "Genome published in 1971"

Repetitive and non-repetitive DNA sequences and a speculation on the origins of evolutionary novelty.

Abstract: Recent experimental information on DNA sequence repetition is reviewed, and the significance of both repetitive and non-repetitive sequence considered. Included are a summary of data on the distribution of genome sizes in animals, new experiments on interspecific DNA homology, the distribution of sequence frequencies, and the interspersion of repetitive sequences within the genome. Aspects of the process of evolution are considered at the level of change in the DNA. the process by which novel structure and function could have arisen during evolution are considered speculatively in terms of the authors' gene regulation theory (Britten and Davidson, 1969).

Location of satellite and homogeneous DNA sequences on human chromosomes.

Abstract: HUMAN DNA1,2 contains at least two satellite fractions—satellite I (0.5% of the genome) which bands at a density of 1.687 g/cm3 in neutral CsCl and satellite II (2% of the genome) which bands at 1.693 g/cm3. The main band DNA has an average buoyant density between 1.670 and 1.720 g/cm3 and a light shoulder (constituting 15% of the genome) with a buoyant density of 1.696 g/cm3, referred to as homogeneous mainband. Satellite DNA has been observed in many higher organisms3, usually with an unknown function, notable exceptions being cistrons coding for ribosomal RNA4 and the DNA coding for histone messenger RNA5. To investigate possible functions of human repetitive DNA we have studied the annealing of complementary RNA fractions to chromosomes using in situ hybridization6,7. We describe here preliminary observations using human satellite II and homogeneous mainband fractions.

Rescue of the Genome of Focus Forming Virus from Rat Non-productive Lines by 5′-Bromodeoxyuridine

Abstract: THE rescue of the genome of transforming RNA viruses from non-productive permissive or non-permissive cells has been achieved by various biological methods, the two basic principles of which are superinfection with leukaemia helper virus1 in the case of permissive cells and mixed culture with homologous cells in the case of non-permissive cells2.

Transcription of Nonrepeated DNA in Mouse Brain

Abstract: Under normal conditions of DNA renaturation, about 60 percent of mouse DNA fragments renature at a rate consistent with their being present only once per sperm. These nonrepeated sequences (also called single-copy or unique) may be used in RNA-DNA hybridization experiments to provide quantitative estimates of RNA diversity. About 10 percent of the mouse single-copy sequences are transcribed in mouse brain tissue. Estimates of about 3 percent were obtained for mouse liver and kidney RNA's. If only one of the complementary DNA strands is transcribed, this hybridization value implies that the equivalent of at least 300,000 different sequences of 1000 nucleotides are expressed in mouse brain tissue. It is suggested that the large amount of DNA in mammals is functionally important, and that a substantial proportion of the genome is expressed in the brain.

Genetic regulation of meiotic chromosome pairing by chromosome 3D of Triticum aestivum.

Abstract: IN hexaploid wheat (Triticum aestivum, 2n = 6x = 42) the constituent genomes A, B and D derive from closely related diploid species (2n = 2x = 14) within the sub-tribe Triticinae1–4. The seven different chromosomes of each genome have genetically equivalent (homoeologous) chromosomes in the other two genomes5. Homoeologous chromosomes generally compensate each other in nullisomic-tetrasomic combinations5.

Comparative DNA Renaturation Kinetics in Amphibians

Abstract: Amphibian haploid genome sizes vary from 9 × 108 to 8 × 1010 nucleotide pairs. The rate of reassociation of DNA from amphibians of different genome sizes has been employed to eliminate one of the theoretical models of chromosome structure. Scaphiopus couchi, Bufo marinus, and Rana clamitans, whose haploid genome sizes are in the ratio 2:7:10, all contain sequences of DNA represented once in the haploid genome. This indicates that their chromosomes are not composed of identical lateral strands (polynemy). The relative frequencies of repetition of DNA sequences are different for the various species of amphibians. The observed frequencies of repetitive DNA sequences in amphibians do not show the relationships expected if amphibians form a polyneme series.

[12] Isolation of mutants from Euglena gracilis

Abstract: Publisher Summary This chapter discusses the isolation of mutants from Euglena gracilis . Most mutations observed in Euglena are nonchromosomal, leading to a consideration of the mitochondrial and plastid genomes. Euglena is an obligate aerobe and cannot grow by fermentative processes; therefore, all mitochondrial mutations, which affect function, are lethal in the dark. There are more than 500 mitochondria per cell, and the probability of segregation of a mutation present in any one mitochondrion is very small. Although mutation of the mitochondrial DNA occurs (aberrant mitochondria are occasionally seen in electron micrographs of mutagenized cells), it is unlikely that any of these could be recovered as mutant cell lines. These arguments also apply to any mutations in the chromosomal or mitochondrial genomes that produce gene products affecting the chloroplast. Experimental evidence suggests that mutations of the chloroplast genome can be detected. Mutant strains might represent clones derived from cells in which all but one of the plastid genomes were prevented from replicating by the mutagenic treatment, and a mutation was induced in the one surviving genome. This mutated genome could then have replicated several times to produce a cell in which all of the chloroplast genomes carried the mutation. It seems likely that the mutants expressed as plastid phenotypes in Euglena are mutations or deletions of the plastid DNA. This is consistent with the observation that the plastid of Euglena is more sensitive than the viability of the cell to alteration by most environmental agents.

Isolation of Transducing Particles of ϕ80 Bacteriophage That Carry Different Regions of the Escherichia coli Genome

Abstract: It has been possible to mate two strains harboring F-prime (F′) factors and to isolate from such matings rare recombinants that behave as though the two episomes had fused. Thus, two genes not previously linked may be brought into close proximity. An F′ factor carrying the attachment site for ϕ80 was fused with one carrying the met-ppc-arg region of the chromosome. Lysogenization of such a strain, followed by induction, led to the isolation of ϕ80arg+ and ϕ80met+ transducing phages. This technique may be utilized as a general method for joining diverse bacterial genes to the genome of phage ϕ80.

Immunological tolerance to rna tumor virus genome expressions: significance of tolerance and prenatal expressions in embryogenesis and tumorigenesis

Abstract: The RNA tumor viruses are clearly different from other myxoviruses; although identified so far in only eight or nine animal species (TABLE l ) , widespread distributions in these species are implied by their generally covert behavior and uniquely compatible relationships with their host cells, being more likely to promote than to hamper cell growth. They have a number of other unique expressions including interspecies as well as intraspecies group-specific (gs) antigens, RNA polymerases that make DNA, and a variety of oncogenic manifestations that occur naturally and that can in large measure be reproduced in laboratory systems. Since each of the various phenotypic expressions of the RNA viral genomes is apparently coded for by different viral genes,', any consideration of immunological tolerance to the RNA viruses must include dealing with a complex group of antigenic moieties and other protein products of these viral genes. Unfortunately, the immunologic complexity exhibited by the RNA tumor viruses is not lessened by their frequently covert behavior, which is largely determined by host cell gene regulators of the viral genes (virogenes) and tumor-inducing genes (oncogenes) 3 , or by the fact that endogenous hormones and exogenous environmental physical and chemical carcinogens also affect the character and degree of virogene and oncogene expressions. In this dissertation we will be mostly concerned with the natural occurrences of the subinfectious group-specific antigens of the C-type RNA tumor viruses in mice, hamsters, cats, and chickens and of immunological tolerance to these antigen~.~-ll These studies were made possible by the recent development of serological techniques (complement fixation (CF),5, 12-16 fluorescent antibody (FA) ,17-19 and gel diffusion l o p 20, 21) for detecting the gs and type-specific envelope (V) antigens in the virions and also in normal and neoplastic tissues, most of which are free of infectious virus particles. Sensitive in vitro tissue culture procedures such as the COFAL,l* COMUL,l5, l6 COCAL,22. 23 and XC 24 tests and various in vivo assays (TABLE 2 ) were utilized to establish the absence as well as the presence of infectious RNA virus. Such tests were also extremely useful in defining the true natural histories of the C-type virus genomes in low as well as high leukemia incidence strains of laboratory mice, chickens, hamsters, and also in free-living (feral) mice and cats. Electron micro~copy,*~~ 26

Mismatching and the Reassociation Rate of Mouse Satellite DNA

Abstract: THE correlation between kinetic complexity and analytical complexity (genome size) established for the nucleic acids of viruses and bacteria and for the “single copy” DNA of a few higher organisms1, 2 has been widely assumed to hold also for the families of repeated sequences found in eukaryotic chromosomal DNA1, 3, 4. This assumption leads to some surprising conclusions: quite closely related species seem to differ greatly both in the proportion of the genome made up of repeated sequences and in the apparent complexity of these sequences1, 4, 5.

Homology of Double Stranded RNA from Rat Liver Cells with the Cellular Genome

Abstract: At least twenty per cent of the double stranded RNA extracted from rat liver hybridizes specifically with rat liver DNA. Some, if not all, of this RNA must therefore derive from transcription of the cellular genome and not from replication of a latent virus.

A comparison of genome sizes and thermal-denaturation-derived base composition of DNAs from several members of Entamoeba (histolytica group).

Abstract: The DNA base composition and genome size of several strains of Entamoeba that form mature 4-nucleated cysts (histolytica group) was compared. These 2 measurements of genetic potential were used to differentiate species. Significant differences in genome size were observed for "classical" E. histolytica, E. histolytica-like amebae, and E. moshkovskii. Significant differences in DNA base composition were found in strains of amebae thought to be of the same species. These data clearly indicate the existence of more than one genospecies for classical E. histolytica, E. histolytica-like amebae, and E. invadens. Members of the genus Entamoeba can be readily divided into four major morphological groups on the basis of the existence or absence of a cyst stage and by the number of nuclei in the mature cyst. One group is characterized by having uninucleated cysts, another has 4-nucleated cysts, a third has 8-nucleated cysts, and one is without any known cyst stage. Levine (1961) conveniently designates these groups as bovis, histolytica, coli, and gingivalis, respectively. Within each of these groups separation into species is especially difficult. Currently, the classification is based primarily on morphology, host specificity, and pathogenicity. This system is inadequate. There are few consistent morphological differences among members of a group other than size. Host specificity is not a particularly reliable character, and pathogenicity is a highly variable property. Additional criteria for classification must be sought. In recent years, advances in our knowledge of the biology of the Entamoeba, gained primarily through study of monoxenically and axenically cultivated organisms, gives promise that the antigenic, biochemical, metabolic, and physiological properties of the amebae can be used to develop more meaningful systems of classification as has been done for bacteria. We have been characterizing entamoebal DNA and using specific differences as a means of distinguishing members of the histolytica group, or those Entamoeba forming 4-nucleated Received for publication 1 December 1970. cysts. In our previous study (Gelderman et al., 1971) we demonstrated that three members of the group, classical Entamloeba histolytica, E. histolytica-like ameba, and E. moshkovskii were sufficiently different with respect to genome size, DNA reassociation kinetics, mole per cent guanine plus cytosine (%GC), and DNA to DNA homologies to be considered distinct species. In that work only one strain of each type was studied. In this study, the results of two parameters of genetic potential (genome size and %GC) are reported for several strains of the histolytica group. GENOSPECIES AND TAXONOMY The ideal taxonomic classification must consider the widest possible range of relatedness such as morphology, host specificity, metabolism, growth requirements, immunological characteristics, specific isozymes, and DNA composition. Many of the parameters change with differing environmental conditions, thus requiring a different part of the DNA to be expressed. However, genome size and %GC of a cell is a biological constant and any significant change in the nucleotide composition of the DNA of an organism with 107 to 108 nucleotide pairs would be lethal to the cell. The DNA base ratio has been extensively studied in bacteria and used as a taxonomic tool (Mandel, 1969). The %GC of the DNA from all bacteria studied varied from 27 to 72%(Shapiro, 1968). The range of the DNA base ratios from the whole family of Enterobacteriaceae varied by only 20% (Shapiro, 1968). The

Simian Virus 40 Integration Site in an Adenovirus 7-Simian Virus 40 Hybrid DNA Molecule

Abstract: The E46+ strain of Adenovirus 7 is a mixed-virus population containing defective Adenoviurs 7-SV40 hybrid particles and helper, nonhybrid Adenovirus 7 particles. We have applied electron microscopic mapping techniques to obtain a physical map of the genome of the hybrid particles present in E46+PL1, a substrain of E46+ derived from a single two-hit plaque. DNA molecules extracted from purified E46+Pl1 virions were found to be linear duplexes, with a mean lenght of 10.9 μm. When these molecules were denatured and renatured, a unique heteroduplex was formed that presumably derived one of its strands from an Adenovirus 7-SV40 hybrid molecule and the other from a nonhybrid Adenovirus 7 molecule. This heteroduplex was double-stranded, except for a short region near one end where the two strands were not paired. On the basis of measurements of the lengths of the single-and double-stranded regions in the heteroduplex, the structure of the Adenovirus 7-SV40 hybrid genome can be reconstructed as follows: The hybrid genome contains 16% less Adenovirus 7 DNA than the nonhybrid Adenovirus 7 genome. This deletion consists of the segment of DNA that maps between 0.05 and 0.21 molecular lenghts in the nonhybrid Adenovirus 7 DNA molecule. The deleted DNA has been partially replaced by an amount of heterologous DNA equivalent to 75% of the complete SV40 genome. A model for the generation of the hybrid genome is presented.

C-Type RNA Tumour Virus Genome Expression in Wild House Mice

Abstract: The presence of the indigenous latent C-type RNA tumour virus genome can be demonstrated in wild house mice by detection of gs antigen and C-type particles. There seems to be strong suppression of the activity of this viral genome in this feral species.

II. Established diploid cell lines of Drosophila melanogaster as potential material for the study of genetics of somatic cells.

Abstract: It can be predicted that the study of genetics of somatic cells will develop considerably in the near future. After the spectacular breakthrough of molecular genetics, the time has come to apply its main results, relating to the function and regulation of the genome of bacteria and viruses, to eukaryotic cells. Many leading biologists have already undertaken a reconversion to different eukaryotic systems, but, in their search for the proper material, all the laboratories have used mammalian or, at least, vertebrate cells. The established lines of diploid cells that Echalier and Ohanessian (1969) have recently grown from embryos of Drosophila melanogaster may offer many advantages in this new field.

The number and location of genes for 5S ribonucleic acid within the genome of Drosophila melanogaster.

Abstract: DNA was prepared from wild-type and two mutant stocks of Drosophila melanogaster that differed in their dosage of the nucleolar organizer region. The relative amounts of DNA from the nucleolar organizer region in these preparations of DNA were determined by hybridization with 3H-labelled 28S rRNA. As expected, the amount of 3H-labelled 28S rRNA that hybridized was directly related to the dosage of nucleolar organizer region. No positive correlation was observed between the amount of 3H-labelled 5S RNA that hybridized and the dosage of nucleolar organizer region. Thus genes for 5S RNA are located primarily, if not exclusively, outside the nucleolar organizer region. The haploid genome of the wild-type D. melanogaster used in this work has 106 genes for 28S rRNA and 96–105 genes for 5S RNA.

Cytosine at the 3'-termini of reovirus genome and in vitro mRNA.

Abstract: DOUBLE stranded RNA isolated from purified reoviruses consists of a mixture of ten different genome fragments1. We have shown that a unique 5′-terminal sequence, ppGpYp (Y = pyrimidine), is present in all ten segments, indicating that they exist as distinct entities within the virion (A. K. S. and A. J. S., manuscript submitted for publication). The duplex segments are transcribed in vitro by a virion-associated RNA polymerase and the resulting single stranded mRNAs also terminate with 5′-ppGpYp2. In view of the similarity between the 5′ ends of reovirus genome RNA and in vitro mRNA, it was of interest to compare their 3′-termini. We now report that both types of RNA have cytosine as the 3′-terminal base.

In vitro synthesis of tRNA Tyr precursors and their conversion to 4S RNA.

Abstract: Three bacterial-specific RNA messengers, transcribed in vitro from phage ϕ80psu3 DNA, contain the nucleotide sequence corresponding to the tRNATyr gene carried by this phage. As there is only one copy of this gene in the phage genome, there are thought to be three promoter sites on the DNA template.

Induction of α-Glucosidase in Mycoplasma laidlawii A

Abstract: MYCOPLASMA are a group of microorganisms distinct from bacteria, blue green algae and viruses. In size, their genomes are intermediate between those of viruses and bacteria and similar to those of the trachoma agents1. We report here the discovery of an α-glucosidase inducible by maltose in Mycoplasma laidlawii A. This is the first demonstration of enzyme synthesis control in the order Mycoplasmatales.

The Investigation of Oncogenic Viral Genomes in Transformed Cells by Nucleic Acid Hybridization

Abstract: Publisher Summary This chapter surveys the knowledge that has been obtained so far, by the use of the nucleic acid hybridization techniques, on the location, state, and functioning of viral genes in cells transformed by polyoma virus, SV40, and adenoviruses. In most of the experiments, hybridization technique is used that consists of immobilizing single-stranded DNA on a nitrocellulose filter and incubating the DNA filter with radioactive single-stranded DNA or RNA in solution, under temperature and salt conditions that favor the formation of specific hybrid complexes. The amount of complex formed is measured by counting the amount of radioactive DNA or RNA, which is bound to the DNA on the filter. Hybridization techniques for the detection of viral-specific nucleotide sequences in the cellular genome must be endowed with a high degree of sensitivity. The nucleic acid hybridization experiments described in the chapter have supplied evidence that viral DNA persists in the transformed cell and its descendents. There is no a priori reason to assume that the state of the viral genome is identical in all transformed cells, or that it is irreversibly fixed in any one line of transformed cells. Under some conditions, the genome may be released from its site on the chromosome and be converted into an extrachromosomal, self-replicating form.

Presence of two DNA populations in Mycoplasma laidlawii.

Abstract: The presence of a DNA population having a molecular weight of 38 ± 5 × 106 in addition to the cellular genome, 99 ± 5 × 107 daltons, in Mycoplasma laidlawii B is evidence for the existence of a satellite DNA or virus intrinsic to these cells.