Genetic Engineering of Plants Agricultural Research Opportunities and Policy Concerns (1984) / Chapter Skim
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Gene Transfer
Gene Transfer
Pages 15-26
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From page 15... ...
DNA contains hereditary information but the major question is how is that information processed and turned into a trait? The answer lies in the "central dogma" of molecular biology- that is, information con15
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The double-stranded DNA helix unwinds and each strand serves as a template for the building of a complementary strand. The resulting daughter DNA molecules are exact copies of the parent, with each double helix having one of the parent strands.
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Next, the messenger RNA moves from the cell nucleus to the cytoplasm. There ribosomes attach to the messenger RNA and direct protein synthesis by reading the genetic code and building a chain of amino acids.
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Here the RNA specifies the sequence of amino acids in a protein according to the triplet codes mentioned earlier. The Technique In theory, gene-splicing is relatively straightforward.
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Hpa 1 does not leave "sticky ends"; it recognizes the sequence CGATT^=c and cleaves each strand between the A and T Restriction enzymes can be used to isolate single genes.
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As the plasmid replicates inside the host cell, it copies the foreign gene along with its standard gene allotment. The goal is not just to clone the gene, but to have that gene expressed—to have the DNA transcribed to RNA, and the RNA translated into the desired protein in the host cell.
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From page 21... ...
Moreover, it comes equipped with a trait molecular biologists were seeking: its genes can be expressed in the environment of the plant genome; the regulatory signals of the bacterial genes can be read by the plant cell. Several scientists reasoned that the Ti plasmid could be tricked into carrying additional genes into the plant genome as well.
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From page 22... ...
The Ti plasmid containing the altered T TUNA region can then he llCt°~ to insert the H~cirPH ~PnPc into plant chromosomes. ~ _ _ _ _ _ ~ ~ ~ ~ ~ ~ _ ~ ~ ~ ~ ~ _ _ _ v ^^ _ ~ ~t~ _ ~ ~ ~ v ~ has been performed by two research groups: one led by Mary Dell Chilton at Washington University and the other a European group led by Jeff Schell of the Max Planck Plant Breeding Institute in Cologne, Germany, and Mark Van Montagu of State University in Ghent, Belgium.
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From page 23... ...
In most work to date, only a small percentage of plant cells inoculated with Agrobacterium carrying the Ti plasmid are transformed. if the Ti plasmid is to be used in a practical gene-transfer system, then much higher rates of transformation must be achieved.
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From page 24... ...
The potato spindle viroicT, for example, contains only 359 nucleotide base pairs, as opposed to about 8,000 in the cauliflower mosaic virus. Gene Expression Until recently, one of the key uncertainties of genetic engineering was whether a foreign gene would be correctly expressed in a higher organism.
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From page 25... ...
Single and Mulligene Traits Based on the recent advances in identifying and isolating genes as well as advances with vectors, many molecular biologists are confident that they will be able to engineer traits controlled by a single gene or a small cluster of genes. Yet many commercially valuable traits, such as yield and stress resistance of various kinds, are controlled by numerous genes somehow acting in concert.
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From page 26... ...
In working with unresponsive species, biologists are often confined to juggling these factors perhaps screening hundreds of genotypes in search of one that will work. To a lesser degree, similar uncertainties surround the other two in vitro regeneration techniques: callus and suspension culture (see Cell Culture, p.
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