New Directions for Biosciences Research in Agriculture High-Reward Opportunities (1985) / Chapter Skim
Currently Skimming:
2. Molecular Genetics and Genetic Engineering
2. Molecular Genetics and Genetic Engineering
Pages 11-31
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 11... ...
From this point any number of creative manipulations can be employed to learn more about the transfer of desirable genes and the enhancement of traits, including those of food animals and crop plants. Combined with conventional plant and animal breeding techniques and the knowledge provided through the collaborations of geneticists, biochemists, immunologists, molecular biologists, pathologists, and virologists, the two techniques create a solid foundation for basic research and for application in treatment and in the diagnosis of both inherited and pathogenic disease.
|
From page 12... ...
It is an arduous task that researchers have rendered somewhat easier by the creation of gene libraries for organisms. To prepare a gene library the DNA of the organism is cut, using selected restriction enzymes that recognize a specific sequence of bases and then snip the strands between particular bases.
|
From page 13... ...
me restriction enzyme is also used to prepare a length of DNA containing an isolated gene. When the cut plasmid and the isolated gene are mixed together in the presence of DNA ligase -- an enzyme that rejoins cut ends of DNA molecules -- the isolated gene fragment is incorporated into the plasmid ring.
|
From page 14... ...
In vitro analyses can yield much basic information on factors contributing to successful genetic manipulations; however, in viva studies ultimately must be conducted in both plants and animals as well as in microorganisms. Opportunities in the Plant Sciences me knowledge base supporting genetic engineering technology for the transfer and expression of foreign genes in crop species is limited.
|
From page 15... ...
Fatty acid synthesis, aromatic amino acid synthesis, biological nitrogen fixation, and carbon fixation are traits currently under investigation in a number of laboratories. Transposable elements, bits of mobile genetic information, were first recognized in maize and are now known to be present in many different organisms.
|
From page 16... ...
Gene Transfer In animal and bacterial systems the availability and early characterization of viruses and bacteriophages that naturally integrate into the genome of the host aided in the development of viral vectors that carry recombinant DNA into these host organisms. Most plant viruses are RNA viruses; the genetic information is carried by RNA rather than DNA.
|
From page 17... ...
, which is transferred by an unknown mechanism into the chromosome of the host plant. After researchers understood that the disease caused by these bacteria was the result of insertion of plasmid T DNA into the plant chromosome, these plasmids were adapted for use in the first-generation plant genetic engineering experiments.
|
From page 18... ...
Viruses or viral sequences might be used to increase the efficiency of gene transfer. After entering the cell the recombinant DNA-containing viral sequence could replicate, increasing the probability that one or more copies of the gene would be integrated into~the genome.
|
From page 19... ...
They should be applicable to all plants and they avoid incorporation of the accompanying DNA of a potentially pathogenic vector. Cell Culture and Plant Regeneration As important and exciting as the recent advances have been in developing vectors for use in plant gene transfer, major challenges remain.
|
From page 20... ...
Nevertheless, the development of a firm scientific and experimental basis in the physiology, topology, biochemistry, and genetics of plant morphogenesis, including normal and somatic embryogenesis, will make an important contribution to several areas of agricultural biology, not least of which is the area of gene transfer Gene Expression me comparison of gene structures has yielded some insights into the factors governing expression of plant genes. What is known about expression, however, is greatly exceeded by what remains unknown.
|
From page 21... ...
To a more limited extent, the same is true for cauliflower mosaic virus; regulatory sequences from this virus, when used in a T DNA-based transformation system, have been demonstrated to function as a regulatory signal in genera that are not considered to be hosts for the virus. The regulatory sequence flanking the nuclear gene that encodes a small subunit of the photosynthetic enzyme ribulose-l,S-bisphosphate carboxylase/oxygenase in peas also functions in the petunia.
|
From page 22... ...
The current system using the Ti plasmid requires weeks to months to obtain results from a gene transfer experiment. A so-called transient expression assay system might be developed by using modified plant viruses as promoter vectors for individual plant cells.
|
From page 23... ...
m e agency must be particularly committed to focused research on important crop plants, the maintenance and use of germ plasm collections, and the high-risk, multidisciplinary research that is essential in bringing newer biotechnologies into practice. To improve the available technology and the efficiency of gene isolation and molecular cloning in plants, special attention should be directed toward the following: 0 Characterization of the biochemical basis and genetic traits involved in important plant processes such as photosynthesis, carbohydrate partitioning, yield, heterosis, stress tolerance, and morphogenesis; · Molecular characterization of mobile genetic elements, such as transposable elements, plant viruses,
|
From page 24... ...
Aspects of Molecular Genetics of Food Animals The knowledge base supporting genetic engineering technology for animals is extensive. Much of the biochemical and molecular genetic understanding of mammalian systems has been achieved through research on human cell culture lines and the laboratory mouse.
|
From page 25... ...
Successful incorporation of the recombinant DNA at this one-cell stage establishes the foreign gene throughout all cells in the resulting animal, including cells of the germ line that give rise to future generations. Mouse populations have been produced that contain recombinant oncogenes or genes coding for thymidine kinase, rabbit beta-globin, human leukocyte interferon, chicken transferrin, or rat growth hormone.
|
From page 26... ...
me concentrations of growth hormone in some of the tranagenic mice were greatly elevated, and as a result the animals grew substantially larger than normal mice. Growth hormone supplied exogenously to mice and some food animals has a dramatic effect in increasing growth rate.
|
From page 27... ...
Such recombinant provirus DNAs can be cloned and used as vehicles for inserting the foreign gene into a host animal cell. The advantage of proviruses as gene transfer vectors is the efficient, transposon-like mechanism by which they can be integrated into the chromosomal DNA of host cells.
|
From page 28... ...
In addition, the discovery of restriction enzyme polymorphisms would provide exceedingly useful markers for genetic analysis in animal breeding studies. Additional information for identifying and isolating specific genes might be compiled through cross cloning, which makes use of a DNA gene probe from one species to hunt for a comparable gene in an organism belonging to another species or genus.
|
From page 29... ...
The ARS has a well-established research effort at Beltsville, Maryland, on gene transfer in food animals. This and related areas of molecular genetic research should be expanded during the next several years, with particular emphasis on the following: Many of the · Characterization of the physiological basis and genetic traits involved in important animal processes such as disease resistance, the immune response, metabolic regulation of nutrient utilization, developmental biology, and other aspects of production efficiency.
|
From page 30... ...
Agriculture Modern genetic technology, including recombinant DNA and the ability to isolate, transfer, and express foreign genes in crop plants and food animals, will likely have an impact on agriculture comparable to that of the discovery of the laws of inheritance in the late 1800s. Improved species with new capabilities might be developed.
|
From page 31... ...
31 hensive screening for useful traits is becoming more widespread, due in part to the influence of genetic engineering. Increasing interest is also being generated in other areas of basic plant and animal sciences, including biochemistry, physiology, pathology, and development, where genetic engineering tools serve as key adjuncts to more traditional research methods.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.