Appendix A - Biotechnology Primer
Genetic Engineering. Every cell contains the full set of genetic information
(genome) needed to reconstruct the entire organism. The information (gene) for
making each cell product is encoded as a specific sequence of nucleic acids in a
specific part of a long DNA molecule. The DNA is used as a template for the
production (transcription) of a messenger-RNA molecule, which carries the
message from the nucleus, where the DNA molecules are located, to the protein-building apparatus (ribosomes) where the specified proteins are made
(translation).
It is now possible to genetically engineer new transgenic organisms by moving
the genes coding for useful characteristics from one organism to another.
Typically, the original DNA molecules are first cut into fragments by special
enzymes (restriction endonucleases). Next the desired fragments are inserted into
bacteria. As the bacteria grow, the new DNA-message is copied (cloned) and
amplified many times. These genes can then be "harvested" and spliced into vectors, organisms that can transfer the gene to the target animal or plant. If
appropriate reading instructions (control sequences) are also transferred, the gene
can function normally, ordering the production (expression) of its proteins in its
new (transgenic) host. Such precise gene transfer differs markedly from classical
sexual breeding where the genes of both parents can be shuffled pretty much at
random.
Plant Tissue Culture. Various auxiliary biotechnologies can facilitate and expand
the usefulness of such manipulations. For example, plant cells can be grown by the
millions in plant tissue culture (PTC), where they can be easily studied,
manipulated and selected for superior traits -- without waiting a full season for the
plants to grow. Often the rigid cellulose cell walls are first removed, leaving bare protoplasts. Using special chemical messengers (hormones), each cell can then be regenerated into a full plant and grown normally in the field.
Monoclonal Antibodies. Other important biotechnologies involve immunological
techniques. The entrance of a recognizably foreign substance (antigen) into the
body triggers a defensive immune response, in which special white blood cells
(lymphocytes) produce antibody proteins to neutralize the intruder. If a cell
producing a specific desired antibody can be located, it can be fused with a rapidly
growing cancer cell to produce hybrid cells that churn out large quantities of that
specific (monoclonal) antibody. Since antibodies lock onto their corresponding
antigens, as a lock fits a corresponding key, these monoclonal antibodies make
excellent probes to detect the presence of their antigens. ELISA (enzyme-linked
immunosorbant assay) diagnostic tests are particularly sensitive. First special
organic catalysts (enzymes) are attached to the antibodies. Antibodies not locking
onto their antigens are flushed away, and then appropriate reactants are added. The
remaining antigen-immobilized enzyme (if present) catalyzes the reaction,
producing large amounts of detectable products to signal the antigen's presence.
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