Showing papers on "Genome published in 1969"
TL;DR: Direct support for the idea that regulation of gene activity underlies cell differentiation comes from evidence that much of the genome in higher cell types is inactive and that different ribonucleic acids are synthesized in different cell types.
Abstract: Cell differentiation is based almost certainly on the regulation of gene activity, so that for each state of differentiation a certain set of genes is active in transcription and other genes are inactive. The establishment of this concept (1) has depended on evidence
indicating that the cells of an organism generally contain identical genomes (2). Direct support for the idea that regulation of gene activity underlies cell differentiation
comes from evidence that much of the genome in higher cell
types is inactive (3) and that different ribonucleic acids (RNA) are synthesized in different cell types (4).
1,898 citations
TL;DR: A density analysis of DNA extracted from a mixture of virus particles containing either bromodeoxyuridine-substituted or unsubstituting DNA shows that virions contain single-stranded DNA which, when released, forms duplex structures.
Abstract: Extracted adenovirus-associated virus DNA is known to be double-stranded, and, therefore, it has been assumed that these virus particles contain a double-stranded genome. Recent findings, however, have suggested that the DNA in virus particles is equivalent to only half the molecular weight of extracted molecules. A density analysis of DNA extracted from a mixture of virus particles containing either bromodeoxyuridine-substituted or unsubstituted DNA shows that virions contain single-stranded DNA which, when released, forms duplex structures. A similar circumstance is as yet unknown among other viruses.
178 citations
TL;DR: It is shown that the rapidly-sedimenting form found in T7-infected cells is, in fact, T7 DNA, that it represents a true intermediate in the production of progeny T8 DNA molecules, and that it sediments more rapidly because it is longer than mature T7DNA.
127 citations
TL;DR: Detailed microscopic studies of the contour length of DNA from a mycoplasma species have shown that the DNA in this organism is organized in a single circular chromosome, 262 microns long, corresponding to a molecular weight of 5.0 × 108 daltons.
Abstract: ELECTRON microscopic studies of the contour length of DNA from a mycoplasma species, Mycoplasma hominis (H 39)1, have shown that the DNA in this organism is organized in a single circular chromosome, 262 microns long, corresponding to a molecular weight of 5.0 × 108 daltons. The genome size of bacterial DNA is only well known for a very few bacteria (genome sizes, 0.8–3.0 × 109 daltons)2, but the genomes in mycoplasmas may well be smaller that those of most or all bacteria. If all or most mycoplasmas were to have this same low chromosomal DNA content, the findings might be taken as a strong indication for their having a common phylogenetic origin as well as justifying the placing of mycoplasmas as a separate class of organisms3.
105 citations
TL;DR: The results indicate that genome simplicity extends to other Drosophila species and to a representative of another Dipteran family, and there are variations among Diptera in genome size as inferred from the informational content of nucleotide sequences.
Abstract: A remarkable feature of evolution in the genus Drosophila is the conservation of the basic karyotype. Postulation of Robertsonian centric fusions (ROBERTSON 1916) is sufficient to explain most of the karyotypic rearrangements found in the various species. The fixation of large duplications of genetic material during the evolution of this genus appears to have been rare (STONE 1955). On the other hand, amino acid sequence data for proteins of other organisms indicate that many cistrons have very similar nucleotide sequences, and are presumably related by prior gene duplication (JUKES 1966). Physical studies of DNA of various eucaryotes also suggest that these genomes contain very large families of related cistrons (BRITTEN and KOHNE 1968). The size of such families is often in excess of that inferred from existing protein data (BRITTEN and KOHNE 1968; MCCARTHY 1967; WETMUR and DAVIDSON 1968). This may in some cases reflect the presence of cistrons with similar nucleotide sequences which specify proteins of overtly different functions. It is also likely that some of these families of genes have functions other than the determination of amino acid sequences. In keeping with the cytological studies, the reassociation kinetics of denatured Drosophila melanogaster DNA imply that the genome of this organism is much less complex, in terms of intragenome nucleotide sequence homologies, than those of vertebrates (LAIRD and MCCARTHY 1968b). Estimates made from these measurements suggest that perhaps 90% of D. melanogaster nucleotide sequences are not closely related to others elsewhere in the genome. In light of the extensive diversity within the genus Drosophila (LAIRD and MCCARTHY 1968a) , a detailed analysis of the intragenome homologies of representative species is expected to provide information about the evolution of genomes. In particular, our results indicate that genome simplicity extends to other Drosophila species and to a representative of another Dipteran family. In addition, there are variations among Diptera in genome size as inferred from the informational content of nucleotide sequences. MATERIALS AND METHODS Details of labeling and isolation of DNA and RNA from Drosophila, preparation of filterbound DNA, hybridization and duplex formation procedures, and analytical CsCl pycnography
93 citations
TL;DR: Bacterial genome sizes, determined by deoxyribonucleic acid reassociation kinetics, vary over a 10-fold range, and the smallest studied, Chlamydia trachomatis, had a genome of 6 x 10(5) nucleotide pairs compared to 4.5 x10(6) for Escherichia coli.
Abstract: Bacterial genome sizes, determined by deoxyribonucleic acid reassociation kinetics, vary over a 10-fold range. The smallest studied, Chlamydia trachomatis, had a genome of 6 × 105 nucleotide pairs compared to 4.5 × 106 for Escherichia coli.
78 citations
TL;DR: The results support the idea that the cytoplasmic hereditary factor, ϱ, resides in mitochondrial DNA and that the ϱ- mutations studied correspond to a dispersed sequence modification covering about a half of the total mitochondrial DNA genome, leaving the other half unchanged.
Abstract: In some respiratory deficient cytoplasmic mutants, the buoyant density of mitochondrial DNA is changed to detectable degrees, as compared to that of wild type strain: since this density shift suggests an important modification of polynucleotide sequence in mitochondrial DNA, we examined sequence homology between mitochondrial DNA of the respiratory mutants issued from cytoplasmic or chromosomal mutations. Mitochondrial DNA, nuclear DNA and total RNA were extracted from ϱ+ cells (wild type, respiratory sufficient) and from ϱ- cells (cytoplasmic “petite colonie” mutant, respiratory deficient), and molecular hybridization experiments were carried out between them. When ϱ+ RNA × ϱ+ mitochondrial DNA, formed roughly twice as much hybrids as the heterologous cross, ϱ+ RNA × ϱ1 mitochondrial DNA. Reciprocally, when ϱ- RNA was hybridized to ϱ+ and ϱ- mitochondrial DNA, the homologous cross produced again about twice as much hybrids as the heterologous cross. These results were confirmed by dehydridization-rehybridization experiments: the RNA separated from the hybrids “ϱ+ RNA × ϱ+ mit-DNA” as well as the RNA separated from the hybrids “ϱ+ RNA × ϱ- mit-DNA” were rehybridized either with ϱ+ or ϱ- mit-DNA. A preferential hybridization of ϱ+ RNA with ϱ+ mit-DNA, and of ϱ- RNA with ϱ- mit-DNA was clearly observed. On the contrary, ϱ+ and ϱ- nuclear DNA did not distinguish ϱ+ or ϱ- RNA. The same series of experiments were carried out using a chromosomal mutation,P
7 to p7, leading to the same respiratory deficient phenotype. We found that the p7 mutation did not introduce a detectable change in mitochondrial DNA base sequence. The results support the idea that the cytoplasmic hereditary factor, ϱ, resides in mitochondrial DNA and that the ϱ- mutations studied correspond to a dispersed sequence modification covering about a half of the total mitochondrial DNA genome, leaving the other half unchanged. Alternatively, the results can be explained by a hypothesis in which mitochondrial DNA is a heterogeneous population of the molecules having more or less related sequences and the mutation leads to a selection of certain molecular species. 4 S RNA was found to contain RNA species which hybridize with mitochondrial DNA. The degree of hybridization was very different for ϱ+ and ϱ- S RNA, when they were hybridized with either ϱ+ or ϱ- mitochondrial DNA.
37 citations
TL;DR: The following conclusion may be reasonably drawn as far as wheat and its relatives are concerned: appreciable changes of DNA content might have resulted from chromosome aberrations accumulated in the course of genome differentiation of a common primitive genome at the diploid level.
Abstract: 1. Comparisons were made of DNA content per nucleus in common wheat, artificially synthesized 6x wheat, its parental species and three analyzers.2. DNA content per nucleus in the D genome analyzer was the lowest, B genome had a little lower DNA content than A genome, but the difference between the last two was not significant.3. Ssp. strangulata had a significantly higher DNA value than var. typica of the same species, Ae. squarrosa.4. Two strains of synthesized 6x wheat, ABD No. 1 and ABD No. 13, have nuclear DNA equal to the sum of the DNA contents of their respective parents. Nuclear DNA content of cultivated common wheat (Chinese Spring) is quite the same as that of synthesized 6x wheat, especially ABD No. 13.5. In three subspecies of T. aestivum, vulgare, spelta and macha no significant difference was found in DNA content per nucleus.6. Based on the above facts, the following conclusion may be reasonably drawn as far as wheat and its relatives are concerned:a) Appreciable changes of DNA content might have resulted from chromosome aberrations accumulated in the course of genome differentiation of a common primitive genome at the diploid level.b) The three different genomes, once established, have been appreciably stable and kept the amount of DNA constant either in diploid or polyploid condition.
31 citations
TL;DR: Evidence supports the involvement of the homoeologues of the B and D genomes and the existence of isoenzymatic proteins which are capable of hybridization in the sub-tribe Triticinae.
Abstract: FOUR different manifestations of the concept of genetic similarity have been demonstrated in the sub-tribe Triticinae. Two of these are at the chromosome level and two are at the gene level. Sears1 demonstrated that each chromosome of hexaploid Triticum has two genetically related chromosomes which are undoubtedly of common origin. These related chromosomes or homoeologues can replace one another without causing serious genetic imbalance. This homoeology extends beyond Triticum to the genera Secale2, Agropyron3 and Aegilops4. Cytological similarity of chromosomes was established by Riley and Chapman5 when they demonstrated that particular non-homologous chromosomes of Triticum and of Triticum and Aegilops have the potential to pair or synapse with one another. Similarity at the phenotypic level of gene expression was examined in detail by Sears6 in his study of Neatby's virescent gene. He showed that there exist three genes affecting chlorophyll production in a similar manner. The three genes are carried on the three chromosomes of homoeologous group 3. We have demonstrated similarity at the level of enzymatic gene-products7 and the existence of isoenzymatic proteins which are capable of hybridization. These proteins are produced by a particular rye chromosome, its wheat homoeologue of the A genome and apparently the homoeologues of the other two wheat genomes. Recent evidence, which will be published in detail later, supports the involvement of the homoeologues of the B and D genomes. These four patterns of similarity are compatible with one another.
30 citations
TL;DR: Results show that cistrons for 30S proteins of E. coli can replace those of S. typhosa in the Salmonella genome and in a diploid hybrid with aSalmonella endogenote and an E. bacteria exogenote, both sets of cistron are expressed.
Abstract: Intergeneric mating between Escherichia coli and Salmonella typhosa was used to locate at least three 30S ribosomal proteins near the streptomycin locus in the region of 54 to 66 min of the E. coli map. This procedure utilizes differences in the electrophoretic patterns of 30S ribosomal protein of the parents. The results show that cistrons for 30S proteins of E. coli can replace those of S. typhosa in the Salmonella genome. Moreover, in a diploid hybrid with a Salmonella endogenote and an E. coli exogenote, both sets of cistrons are expressed.
30 citations
TL;DR: By isolating phage mutants that induce low levels of dTTPase, it has been possible to show that one enzyme is responsible for both the activities and that its structure is determined at least partly by the phage genome.
TL;DR: 4-Proline analogues were synthesized and pharmacologically evaluated as a step toward determining whether they occur naturally, and it is concluded that they do not occur naturally.
Abstract: Evolutionary changes in the amino acids in the third and eighth positions of neurohypophysial hormones could result from single base mutations in the genome. Substitution of 4-serine for 4-glutamine requires an intermediate codon, either for termination or for proline. 4-Proline analogues were synthesized and pharmacologically evaluated as a step toward determining whether they occur naturally. (Endocrinology 85: 385, 1969)
TL;DR: Tomato secondary trisomics: Origin, identification, morphology, and use in cytogenetic analysis of the genome and its applications in medicine and science.
Abstract: Tomato secondary trisomics: Origin, identification, morphology, and use in cytogenetic analysis of the genome
TL;DR: After transformation into active compound(s) the L -, D - and meso -isomers of threitol-1,4-bismethanesulfonate can induced chromosomal aberrations in barley and onion root-tips and it was found that quantitative differences also exist when the treatment conditions allow chemical transformation and subsequent mutagenic effects.
Abstract: After transformation into active compound(s) (probably diepoxybutane) the L -, D - and meso -isomers of threitol-1,4-bismethanesulfonate can induced chromosomal aberrations in barley and onion root-tips. Quantitative differences are found between the effects of the isomers ( L > D > meso ), but the 3 forms induce similar qualitative effects as judged by various criteria: the types of aberrations; the location of breaks in heterochromatic or euchromatic segments of the genome in relation to the sampling time; and the relative proportions of breaks in mediocentric chromosomes and satellite chromosomes of onion. The mutagenic activity of the 3 isomers was investigated in Arabidopsis thaliana : it was found that quantitative differences also exist when the treatment conditions allow chemical transformation and subsequent mutagenic effects.
TL;DR: Meiosis in sets of reciprocal hybrids between L. cylindrica and L. graveolens was highly irregular, leading to total sterility, and it is suggested on genetic grounds, that the cultivated L.cylindrica has the basic genome, the wild L.graveolens genome having been derived from it.
Abstract: Meiosis in sets of reciprocal hybrids betweenL. cylindrica andL. graveolens was highly irregular, leading to total sterility. Occurrence of univalents and several types of multivalents indicated considerable differentiation between the genomes. It is suggested on genetic grounds, that the cultivatedL. cylindrica has the basic genome, the wildL. graveolens genome having been derived from it.
TL;DR: Using the technique of DNA-RNA hybridization, the whole PhiX-174 genome is transcribed during concomitant protein synthesis.
Abstract: We have described an in vitro system which couples UTP incorporation into RNA by DNA-dependent RNA polymerase with RNA-directed amino acid incorporation into polypeptides. Using the technique of DNA-RNA hybridization, we have demonstrated that the whole ΦX-174 genome is transcribed during concomitant protein synthesis.
TL;DR: It was concluded that the genome constitution of Mentha aquatica L. with 96 chromosomes was RaRaSSJJA5qA5Q and a genealogical tree of the subgenus Menthastrum was tentatively presented on the basis of the results obtained.
Abstract: Cytogenetical studies of Mentha aquatica L. with 96 chromosomes were carried out by the aid of the interspecific crosses with 4 mint species including 7 strains of the known genome constitutions. It was concluded that the genome constitution of this mint species was RaRaSSJJA5qA5q. In addition, a genealogical tree of the subgenus Menthastrum was tentatively presented on the basis of the results obtained so far.
01 Jan 1969
01 Jan 1969
TL;DR: It is shown that in some SV40-induced tumors the entire viral genome may persist in the transformed cells in a non-infectious and non-antigenic state, suggesting that most virus- induced tumors are characterized by the persistence of a portion of the viral genome as a heritable factor in the transformation cells.
Abstract: Advances in tumor virology and tumor immunology during the past 6 years or so have been characterized by 2 major achievements One was the demonstration that in some SV40-induced tumors the entire viral genome may persist in the transformed cells in a non-infectious and non-antigenic state (1) The other landmark was the discovery in most virus-induced tumors of 2 types of antigens—the transplantation antigens located on the cell surface and the intracellular T- or neoantigens Both of these antigens are considered to be products specified by the viral genome, suggesting that most virus-induced tumors are characterized by the persistence of a portion of the viral genome as a heritable factor in the transformed cells (2)