J. N. Davidson

Bio: J. N. Davidson is an academic researcher. The author has contributed to research in topics: Nucleic acid & Nucleic acid methods. The author has an hindex of 4, co-authored 4 publications receiving 2567 citations.

The nucleic acids

Abstract: Nucleic Acids are another important type of organic compound that is necessary for life. A nucleic acid is a complex biomolecule that stores genetic information in the form of a code. Nucleic acids are so named because they arise from the nucleus of the cell. The nucleus is often referred to as the “control center” of the cell because the nucleic acids within contain the coded instruction for all of the cell’s (and therefore the organism’s) activities.

The biochemistry of the nucleic acids

Abstract: The biochemistry of the nucleic acids , The biochemistry of the nucleic acids , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Sulfolobus : A new genus of sulfur-oxidizing bacteria living at low pH and high temperature

Abstract: Sulfolobus is a new genus of bacteria characterized as follows: 1. generally spherical cells producing frequent lobes; 2. facultative autotrophy with growth on sulfur or on a variety of simple organic compounds; 3. unusual cell wall structure devoid of peptidoglycan; 4. acidophilic, pH optimum of 2–3 and range from 0.9–5.8; 5. thermophilic with temperature optimum of 70–75°C and range from 55–80°C (one strain grew at 85°C). The DNA base composition of five strains was determined by cesium chloride density gradient centrifugation and found to be 60–68% guanine plus cytosine. Sulfolobus apparently has no close relationship with any previously described bacteria, either heterotrophic or autrotrophic. Techniques are presented for distinguishing Sulfolobus from Thermoplasma, another genus of acidophilic thermophilic spherically shaped organisms. Sulfolobus has been isolated from a variety of natural acidic thermal habitats, both terrestrial and aquatic. Most isolations have been from habitats in Yellowstone National Park, but strains were also isolated from Italy, Dominica and El Salvador. It is suggested that Sulfolobus may be an important geochemical agent in the production of sulfuric acid from sulfur in high temperature hydrothermal systems.

Stomatal size in fossil plants: evidence for polyploidy in majority of angiosperms

Abstract: Three published estimates of the frequency of polyploidy in angiosperms (30 to 35 percent, 47 percent, and 70 to 80 percent) were tested by estimating the genome size of extinct woody angiosperms with the use of fossil guard cell size as a proxy for cellular DNA content. The inferred chromosome numbers of these extinct species suggest that seven to nine is the primitive haploid chromosome number of angiosperms and that most angiosperms (approximately 70 percent) have polyploidy in their history.