io9 | Over the past several decades, biologists have refined their
transgenic techniques, including the introduction of DNA microinjection,
embryonic stem cell-mediated gene transfer, and retrovirus-mediated
gene transfer.
More recently, scientists have figured out how to modify the DNA of
plants and animals to much greater degrees of precision. While
techniques using bacterial and viral DNA enabled scientists to transport
genes into the chromosomes of various organisms, the precise target for
where the transgene was to eventually land could not be controlled. The
CRISPR/Cas9 system,
which normally allows the bacterial immune system to store DNA
'fingerprints' of viruses, now enables scientists to choose a specific
region of the genome for either gene disruption (a gene knockout) or
insertion (creating a more-precise transgenic organism).
This
technology is extremely powerful because the original genes of an
organism (its endogenous genes) provide a direct entryway for scientists
to control, or edit, an organism's biology. For instance, if someone
has a mutation that causes a disease in a particular type of cell, using
CRISPR/Cas9 to replace the mutant gene with a normal gene could
theoretically cure that disease. Likewise, it could be used to introduce
a foreign transgene.
So, for example, scientists have used CRISPR/Cas9 to correct B-thalassemia (a condition similar to sickle-cell anemia) in human blood cell lines. They also used it to fix a mutation causing a liver disease in mice
(though their technique only corrected 0.4% of mutated liver cells,
these cells were able to rescue liver function). Additionally,
researchers recently used the technique to create programmable antibiotics that selectively targets undesirable microbes.
Today, transgenic organisms are used for a number of purposes, from
toxicology and the improvement of plants and livestock to the creation
of animals that simulate human diseases. They can be divided into three
major functions:
- To obtain information on gene function and regulation as well as on human diseases
- To obtain high value products (recombinant pharmaceutical proteins and xeno-organs and xeno-tissues for humans) to be used for human therapy
- To improve animal products for human consumption.
As noted by Emily Anthes , author of Frankenstein's Cat, genetically engineered animals could do real good for the world. As she notes in The New York Times,
scientists have created transgenic salmon that can reach their adult
size in a year and a half, rather than three years. There's also the
famous "spider goats" — hybrid goats that secrete exceptionally strong strands of spider's silk, and transgenic glow-in-the-dark pigs and rabbits that use jellyfish DNA (the point of which kind of eludes me).
