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Biology is often approached today on the basis of levels that deal with fundamental units of life. At the level of molecular biology, for example, life is regarded as a manifestation of chemical and energy transformations that occur among the many chemical constituents that comprise an organism. As a result of the development of more powerful and precise laboratory instruments and techniques,...
in biology: Biology in the 20th century )Just as the 19th century can be considered the age of cellular biology, the 20th century has been characterized by developments in molecular biology.
New analytic methods in molecular biology have made genetic studies for the characterization and identification of bacteria more practical. The DNA hybridization technique is an example. A strand of DNA from a known species (the probe) is radioactively labeled and “mixed” with DNA from an unidentified species. If the probe and the unknown DNA are from...
...and biological chemistry. Those aspects of biochemistry that deal with the chemistry and function of very large molecules (e.g., proteins and nucleic acids) are often grouped under the term molecular biology. Biochemistry is a young science, having been known under that term only since about 1900. Its origins, however, can be traced much further back; its early history is part of the...
...material, and in establishing the precisely detailed structure of proteins such as hemoglobin in order that the position of each atom may be known. Biophysics and the intimately related subject molecular biology now are firmly established as cornerstones of modern biology.
...science born in the 20th century, reveals in detail how natural selection works and led to the development of the modern theory of evolution. Beginning in the 1960s, a related scientific discipline, molecular biology, enormously advanced knowledge of biological evolution and made it possible to investigate detailed problems that had seemed completely out of reach only a short time...
in evolution: Molecular biology )The field of molecular biology provides the most detailed and convincing evidence available for biological evolution. In its unveiling of the nature of DNA and the workings of organisms at the level of enzymes and other protein molecules, it has shown that these molecules hold information about an organism’s ancestry. This has made it possible to reconstruct evolutionary events that were...
in evolution: DNA and protein as informational macromolecules )The advances of molecular biology have made possible the comparative study of proteins and the nucleic acids, DNA and RNA. DNA is the repository of hereditary (evolutionary and developmental) information. The relationship of proteins to DNA is so immediate that they closely reflect the hereditary information. This reflection is not perfect, because the genetic code is redundant, and,...
...have replaced earlier structural studies of organ systems. This trend can be explained in part by the fact that the analysis of an organ system typically involves studies at the levels of cells and molecules, and functional emphasis accommodates such studies better than the organ-system approach.
The revolution that took place in the field of molecular biology allowed the genetic information encoded in nucleic acids of viruses—which enables viruses to reproduce, synthesize unique proteins, and alter cellular functions—to be studied. In fact, the chemical and physical simplicity of viruses has made them an incisive experimental tool for probing the molecular events involved...
Although the cell was recognized as the basic unit of life early in the 19th century, its most exciting period of inquiry has probably occurred since the 1940s. The new techniques developed since that time, notably the perfection of the electron microscope and the tools of biochemistry, have changed the cytological studies of the 19th and early 20th centuries from a largely descriptive inquiry,...
Swiss botanist and pioneer of submicroscopic morphology, who helped to initiate the study later known as molecular biology.
...of the first type, with which it had been mixed. The results of this research indicated that the substance responsible for the change was DNA. The three men’s work gave rise to the field of molecular biology.
...chemical firm BASF on the synthesis of isoprene (1910), the monomer of which natural rubber is composed. The prevalent belief at the time was that rubber and other polymers are composed of small molecules that are held together by “secondary” valences or other forces. In 1922 Staudinger and J. Fritschi proposed that polymers are actually giant molecules (macromolecules) that are...
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