Transgenic Animals and Plants
Genetic modifications of animals and plants by recombinant DNA technology (transgenesis) entail the introduction of cloned genes into the genome of a cell.
Subsequently, the modified organisms will express the desired characteristics.
Transgenic Animals
Much of the research in this area was centered on developing transgenic mice.
The commonly used procedure includes introducing a cloned gene into a fertilized egg, implanting the treated fertilized egg into a receptive female, and then testing the offspring to determine whether the input gene has been biologically inserted into their cells.
Transgenic Mice
In 1980, J.W. Gordon and his colleagues successfully produced the first transgenic mice by direct injection of cloned plasmid DNA into the pronucleus of a fertilized egg.
The embryos were implanted in the oviducts of pseudopregnant females.
DNA from newborn mice was evaluated for the presence of DNA homologous to the injected plasmid.
Transgenic Mice by Microinjection
Gene Transfer Techniques
Virus A human gene is inserted into a herpes virus, which can infect a human cell, where the gene will be expressed. Retrovirus An RNA virus carrying an RNA version of a human gene infects a somatic cell. The gene is reverse transcribed to DNA and inserted into a human chromosome. Here, it may produce a missing or abnormal protein. Liposome transfer A fatty bubble called a liposome carries a gene into a somatic cell. Here, the delivered gene may replace an abnormal one.
Chemical Calcium phosphate or dextran sulfate opens transient holes in a cell membrane, admitting replacement DNA. Electroporation Electrical current opens transient holes in a cell's membrane, admitting replacement DNA. Mircoinjection A tiny needle injects DNA into a cell lacking that DNA sequence. Particle bombardment Metal pellets coated with DNA are shot with explosive force or air pressuer into recipient cells.
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