Genetic Engineering, Stem Cells, and Cancer Gene Mutation

Transgenic Organisms and Genetic Transformation

Cisgensis refers to the transfer of a gene from the same species into itself—for example, introducing a desired mouse gene into another mouse. In contrast, transgenic organisms result from introducing a foreign species' gene into a different species, such as inserting a jellyfish fluorescent protein gene into E. coli in the laboratory.

Creating transgenic plants involves a multi-step process. First, a DNA segment containing a desired trait is inserted into a plasmid using restriction enzymes and DNA ligase. Next, this recombinant plasmid is introduced into plant cells in culture, where T-DNA carries the new gene into the plant chromosome. Finally, the plant is regenerated, producing an organism with the novel traits.

Agrobacterium is a bacterium that naturally causes tumors on plants; scientists exploit this natural vector for genetic engineering. For example, researchers have inserted scorpion venom genes into cauliflower to prevent caterpillars from feeding on cabbage crops. Similarly, glyphosate—a herbicide that binds to plant enzymes required for protein synthesis—was combined with genetic modification to create Roundup Ready plants. These GMOs express the CP4 EPSOPS enzyme, which confers resistance to glyphosate, allowing farmers to spray the herbicide without killing the crop. This approach is widely used in cotton, soybeans, and corn.

Transgenic trees have been engineered to grow faster for timber production. Monoculture cultivation—the farming of a single crop—presents challenges including reduced genetic diversity and limited adaptive capacity in the face of environmental stress.

Gene knockout involves the eradication of a specific gene, while gene knockin refers to the addition of a new gene, often a resistance gene. Recombinant genes are formed when two or more DNA sequences are combined to create novel genetic material that expresses new traits.

The classic Hershey-Chase experiment demonstrated that DNA, not protein, is the genetic material. In bacterial transformation using plasmids, DNA is inserted into a vector and cut with restriction enzymes at specific sites, preventing uncontrolled replication. The cut DNA is then ligated (joined). When this vector is introduced into a host cell lacking the vector, the cell becomes antibiotic-resistant, allowing scientists to identify successfully transformed cells.

Phage (bacteriophage) vectors offer an alternative to bacteria for DNA delivery. Transfection is the process of introducing genetic material into cells using phage vectors.

Golden Rice represents a landmark achievement in agricultural biotechnology. This genetically modified rice variety is enriched with beta-carotene, a precursor to vitamin A, addressing nutritional deficiency in populations relying heavily on rice as a staple grain.

Transgenic animals are similarly engineered for specific traits. Enviropigs, for instance, were pigs modified to express E. coli phytase enzyme, allowing them to use dietary phosphorus more efficiently. Transgenic salmon have been injected with genes that increase hormone production, though these fish are typically infertile and poorly adapted to natural environments, limiting their ecological viability. In transgenic mice, target genes are introduced into blastocyst-stage embryos. Mating a transgenic mouse with a normal mouse produces offspring carrying the transgene in some cells, though transmission to subsequent generations depends on whether the modification occurred in germ cells.