Opportunities in Biology (1989) / Chapter Skim
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2. New Technologies and Instrumentation
2. New Technologies and Instrumentation
Pages 19-38
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From page 19... ...
The DNA chains exhibit molecular complementarity in that the Gs on one strand always pair with the Cs on the other; likewise, the As always pair with the Ts. This molecular complementarily means that in a mixture of unpaired DNA fragments, one fragment will always be able to find its complement by virtue of the precise pairing of their nucleotide bases.
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From page 20... ...
20 OPPORTUNITIES IN BIOLOGY __ ~_ DNr~A is ~ double A_ strc~n~d helix. The ~_ r~ro strar~C.
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From page 21... ...
The DNA ligases permit any two DNA fragments to be joined together. Accordingly, the essence of the recombinant DNA techniques is the ability to take a DNA fragment containing any particular gene of interest, say a-interferon, and join it into an appropriate vector sequence, such as a plasmid, to create a hybrid or recombinant DNA molecule.
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From page 22... ...
This technic ~ Sled "gem splicing" or recombinant DNA technology FIGURE 2-2 Recombinant DNA Technology. [Figure courtesy of Monsanto]
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From page 23... ...
Several copies of the injected gene will have become integrated into a chromosome of a transgenic mouse, generally in one location, as shown by the Mendelian transmission of the gene to half of its progeny. The transgenic mice that develop from these injected embryos are each potentially the founder of a unique family: Even if the same gene is injected into
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From page 24... ...
The mice of this second line are not sterile, but they are still "big," suggesting that in the long run we may be able to design animals with a desired characteristic but without the accompanying undesirable side effects. Another application using transgenic mice has been the dissection of the regulatory segments of genes expressed in different cell types of the body.
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From page 25... ...
The defects can then be cured by the introduction of normal alleles of these genes. In addition, transgenic mice afford excellent tools for learning about physiology and endocrinology because individuals that Puce particular hormones in unusual quantities can be produced.
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From page 26... ...
Future Prospects The Potentialfor Using Transgenic Organisms to Make Discoveries over the Next 5 or 10 Years Is Vast The techniques of producing ~ansgenic organisms are fast becoming an important part of a wide variety of experimental approaches to questions in biology and medicine. These range from the study of gene regulation, to the development of the immune system, to tests of theories in endocrinology and physiology, to mechanisms of self-tolerance and autoimmune disease, and finally to the study of cancer and other important human diseases.
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From page 27... ...
In medicine the transformation of microbial cells with foreign genes has resulted in the commercial production of such valuable products as insulin, human growth hormone, interferons, and tissue plasminogen activator. MONOCLONAL ANTIBODIES Monoclonal Antibodies Can Be Used as Biological Probes for Specific Molecules Another significant area of biological advance has been the development and application of monoclonal antibodies.
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From page 28... ...
Monoclonal antibodies can then be generated from these immune responses. The use of monoclonal antibodies has revolutionized many aspects of fundamental biology and clinical medicine.
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From page 29... ...
O 000 0\ production | O O O O O 00 ~ O \ Selected hybridomas are cultured Purified monoclonal antibodies 29 f ~ J L / FIGURE 2-3 Production of monoclonal antibodies. [Adapted from J
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From page 30... ...
The ability to sequence very small quantities of protein is important because even limited amounts of protein sequence data can facilitate cloning of the corresponding gene. Currently a variety of new approaches are being used for even more sensitive detection of amino acids, including fluorescent detection, which should permit sequencing of 10 to 100 femtomoles within the next few years.
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From page 31... ...
This sequence can in turn be synthesized as an oligonucleotide fragment that can be used in conjunction with routine recombinant DNA techniques to clone the corresponding gene. FLOW CYTOMETRY Flow Cytometry Is Used to Sort Cells A flow cytometer, also known as a fluorescence-activated cell sorter, is an instrument that quantifies fluorescent molecules bound to individual cells or subcellular particles.
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From page 32... ...
MICROSCOPY A Revolution in the Application of Light Microscopy Has Occurred Advances in light microscopy have resulted from an integration of the fields of microscope optics, video technology, digital image processing, biology, and chemistry. The remarkable advances in the past few years have been driven by the need for biologists to define the dynamics of the chemical constituents in living cells.
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From page 33... ...
Quantitative fluorescence microscopy, when combined with the multitude of biological probes and fluorescent probes now available, offers an approach for gathering complex chemical and molecular information from living cells and tissues. The power of quantitative fluorescence microscopy results from its high sensitivity and specificity, combined with spatial as well as temporal resolution.
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From page 34... ...
Because some fluorescent probes change their spectroscopic characteristics in response to the chemical environment, changes in the pH, the free calcium ion concentration, or other measures can alter the excitation or the emission properties of environmentally sensitive probes. Measuring the fluorescence at two wavelengths can be used to rapidly quantify the pH, the calcium ion concentration, or other specific variables, allowing temporal and spatial changes in these variables to be determined in living cells.
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From page 35... ...
The Atomic Force Microscope Holds Great Promise for Analyzing Biological Specimens Even more informative images of biological molecules may come from the atomic force microscope. In the atomic force microscope, the tip is placed on a cantilever beam, which can deflect as the force on the tip is changed.
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From page 36... ...
Static structural techniques, such as x-ray crystallography, reveal little of these dynamic events; in contrast, magnetic resonance provides a powerful tool for studying dynamics: how enzymes bind substrates, how antibodies bind antigens, how receptors bind ligands. Metabolic events within cells of all Apes can be directly observed by magnetic resonance; it is a completely nondisruptive technique for studying the complex interrelations among metabolic pathways, which is not possible with any other approach.
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From page 37... ...
Moreover, it is possible to take protein sequences and search for patterns of amino acid subunits that correlate with various forms of secondary structure. With the advent of automated DNA sequencing, the DNA data bank will enlarge rapidly.
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From page 38... ...
38 OPPORTUNITIES IN BIOLOGY information analysis and dissemination, funding strategies, training and education, and methods of balancing single-investigator research with that of large research centers. Our success in addressing these challenges will largely dictate the effectiveness of biology research programs in the United States, and hence the contributions of American biologists to the development of the global data base for the field.
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