Transgenic plants such as corn and soybean have replaced wild strains in agriculture in some countries (e.g. the United States).
However, until the late 1900s farmers and scientists could breed new strains of a plant or organism only from closely related species because the DNA had to be compatible for offspring to be able to reproduce.
[citation needed] In the 1970 and 1980s, scientists passed this hurdle by inventing procedures for combining the DNA of two vastly different species with genetic engineering.
[2] The first transgenic organism was created in 1974 when Annie Chang and Stanley Cohen expressed Staphylococcus aureus genes in Escherichia coli.
A variety of transgenic plants have been designed for agriculture to produce genetically modified crops, such as corn, soybean, rapeseed oil, cotton, rice and more.
In 1997,[citation needed] five million children developed xerophthalmia, a medical condition caused by vitamin A deficiency, in Southeast Asia alone.
[7] To combat this, scientists used biolistics to insert the daffodil phytoene synthase gene into Asia indigenous rice cultivars.
[9] The escape of genetically-engineered plant genes via hybridization with wild relatives was first discussed and examined in Mexico[10] and Europe in the mid-1990s.
Seed and grain import from the United States could explain the frequency and distribution of transgenes in west-central Mexico, but not in the southeast.
[14] Transgenic rapeseed Brassicus napus – hybridized with a native Japanese species, Brassica rapa – was found in Japan in 2011[15] after having been identified in 2006 in Québec, Canada.
Knockout mice are a type of mouse model that uses transgenic insertion to disrupt an existing gene's expression.
In order to create knockout mice, a transgene with the desired sequence is inserted into an isolated mouse blastocyst using electroporation.
Through this process, researchers were able to demonstrate that a transgene can be integrated into the genome of an animal, serve a specific function within the cell, and be passed down to future generations.
[24] Oncomice are another genetically modified mouse species created by inserting transgenes that increase the animal's vulnerability to cancer.
While it has shown to have a lower efficiency of transgenic transformation than the P element transposases, Cre greatly lessens the labor-intensive abundance[clarification needed] of balancing random P insertions.
These sites, unlike P elements, can be specifically inserted to flank a chromosomal segment of interest, aiding in targeted transgenesis.
The Cre transposase is important in the catalytic cleavage of the base pairs present at the carefully positioned loxP sites, permitting more specific insertions of the transgenic donor plasmid of interest.
[26] To overcome the limitations and low yields that transposon-mediated and Cre-loxP transformation methods produce, the bacteriophage ΦC31 has recently been utilized.
Recent breakthrough studies involve the microinjection of the bacteriophage ΦC31 integrase, which shows improved transgene insertion of large DNA fragments that are unable to be transposed by P elements alone.
Scientists are focusing on the use of transgenes to study the function of the human genome in order to better understand disease, adapting animal organs for transplantation into humans, and the production of pharmaceutical products such as insulin, growth hormone, and blood anti-clotting factors from the milk of transgenic cows.
[citation needed] Transgenic microorganisms capable of producing catalytic proteins or enzymes which increase the rate of industrial reactions.
The most famous example of this involved certain patients developing T-cell leukemia after being treated for X-linked severe combined immunodeficiency (X-SCID).