An upper limit to the protein content of the germinal substance of bacteriophage T2

Hershey, Alfred Day

doi:10.1016/0042-6822(55)90009-x

Cited by 233 publications

(51 citation statements)

References 12 publications

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“…It was later shown that this substance could be destroyed by the enzyme DNase (Avery et al 1944). In 1955, Hershey and Chase established that the substance actually transmitted by bacteriophage to their progeny is DNA and not protein (Hershey and Chase 1955). Moreover, the idea that a gene's product is a diffusible substance underlies the complementation test that was used to define genes in the early years of bacteriology.…”

Section: Definition 1950s: Gene As a Physical Moleculementioning

confidence: 99%

What is a gene, post-ENCODE? History and updated definition

et al. 2007

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While sequencing of the human genome surprised us with how many protein-coding genes there are, it did not fundamentally change our perspective on what a gene is. In contrast, the complex patterns of dispersed regulation and pervasive transcription uncovered by the ENCODE project, together with non-genic conservation and the abundance of noncoding RNA genes, have challenged the notion of the gene. To illustrate this, we review the evolution of operational definitions of a gene over the past century-from the abstract elements of heredity of Mendel and Morgan to the present-day ORFs enumerated in the sequence databanks. We then summarize the current ENCODE findings and provide a computational metaphor for the complexity. Finally, we propose a tentative update to the definition of a gene: A gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products. Our definition sidesteps the complexities of regulation and transcription by removing the former altogether from the definition and arguing that final, functional gene products (rather than intermediate transcripts) should be used to group together entities associated with a single gene. It also manifests how integral the concept of biological function is in defining genes.

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Section: Definition 1950s: Gene As a Physical Moleculementioning

confidence: 99%

What is a gene, post-ENCODE? History and updated definition

et al. 2007

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“…The strains of E. coli were maintained on nutrient agar slopes containing appropriate drugs at the following concentrations (pg ml-l) : ampicillin, 10; streptomycin, 10; sulphonamide, 50; tetracycline, 10. For closed culture growth, the organisms were grown in nutrient broth or the minimal medium described by Davis & Mingioli (1950) containing 10 , % (w/v) glucose or Hershey's glucose mineral salts medium (Hershey, 1955). The cultures were incubated at 37 "C with vigorous aeration and growth was measured by determining the absorbance (As2,,) in a Corning model 252 colorimeter.…”

Section: Methodsmentioning

confidence: 99%

“…The Davis & Mingioli minimal medium pH 7.0, supplemented with glucose to a growth-limiting concentration of 0.2 g l-l, was used for glucose-limited continuous-flow culture. For phosphate-limited chemostat growth, the organisms were grown in Hershey's glucose mineral salts medium (Hershey, 1955) at pH 7.4 with phosphate at 0.005 g 1-l. The continuous-flow culture vessels had a working volume of 1 I and were agitated at 1000 rev.…”

Section: Methodsmentioning

confidence: 99%

The Influence of the Growth Environment on the Stability of a Drug Resistance Plasmid in Escherichia coli K12

1979

Journal of General Microbiology

198

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201Populations of Escherichia coli K12 containing the plasmid TP120 which coded for resistance to ampicillin, streptomycin, sulphonamide and tetracycline were grown in a chemostat under carbon-limited and phosphorus-limited conditions. With time, resistance to one or more of the drugs was lost, resulting in the production of mutant populations which were more competitive than the parent population. The resistance to tetracycline was always lost under both carbon and phosphorus limitations, but resistance to the other three drugs was lost only during phosphate-limited growth. Strains of E. coli which had lost resistance to one or more of the drugs were capable of higher maximum specific growth rates than the parent strain.

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“…NaC1 per ml. of mixed stock and then rapidly dumping in more than 20 volumes of water (10). The titer was reduced 80-fold over the unshocked controls and the specific viscositY 3 increased to 0.49.…”

Section: Growth and Purification Of P~-labdledmentioning

confidence: 80%

The Release and Stability of the Large Subunit of Dna From T2 and T4 Bacteriophage

Thomas

1959

The Journal of General Physiology

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T2 and T4 bacteriophage have been exposed to various treatments which are known to release the encapsulated DNA. The unseparated reaction products have been examined by autoradiography. The results indicate the presence of one large subunit of DNA (molecular weight 45 × 106) for each former phage particle. Some smaller subunits of molecular weight 12 × 106 have been observed.The large subunit is sensitive to very small amounts of DNAase, and is resistant to mixed proteases and cannot be dispersed by banding in cesium chloride density gradients.The sensitivity to fragmentation by P~ decay and the increase in this sensitivity following heat treatment are best explained by assuming that the large subunit is a duplex of polynucleotide strands over most of its length.The presence of hypothetical non-DNA interconnections is considered.In earlier communications (1, 2) evidence was presented that exposure of T, or T4 bacteriophage to "osmotic shock" (3), a procedure which opens the phage membrane and exposes the enclosed DNA to such agents as DNAase, results in the release of a single large subunit of DNA comprising approximately 40 per cent of the total phosphorus of the phage particle. These conclusions were based on counting "stars" in electron-sensitive nuclear emulsions. The stars which are clusters of/5-ray tracks emanating from highly labelled DNA molecules or virus particles, can be recognized and counted. It was found that there was one large subunit for each phage particle. Within limits, it is also possible to determine the number of fkray tracks making up the star. By an analysis of the population of star sizes, it was surmised that the phosphorus content of this DNA-like fragment was very uniform, and certainly could not have been produced by the random fragmentation of the total DNA in the phage particle. Thus one is led to think that this large subunit pre-*

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An upper limit to the protein content of the germinal substance of bacteriophage T2

Cited by 233 publications

References 12 publications

What is a gene, post-ENCODE? History and updated definition

What is a gene, post-ENCODE? History and updated definition

The Influence of the Growth Environment on the Stability of a Drug Resistance Plasmid in Escherichia coli K12

The Release and Stability of the Large Subunit of Dna From T2 and T4 Bacteriophage

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