There are a lot of labs in biology that are
super memorable, as I’ve mentioned before, but I remember this one where we had these
bacteria and we gave the bacteria a gene from a different organism. It came from a jellyfish- specifically a bioluminescent
jellyfish. Its gene that was taken up by the bacteria
gave the bacteria the ability to have this glowing appearance if put under the UV light. Like the jellyfish. How wild is that? It was a neat lab to do once I became a teacher
too – this is actually a very popular lab in advanced biology courses. But naturally, everyone kept wanting to know,
“Is it possible for bacteria to be given a human gene? Not just one from a jellyfish?” The answer to this class question is yes! And that’s when I got to talk about how
insulin is produced. Insulin is a hormone that all humans need;
it is made by the pancreas. The hormone insulin helps make sure that cells
get the glucose they need. But Type 1 Diabetes is a condition where the
pancreas doesn’t make enough insulin, and therefore the individual must take insulin,
usually in the form of an injection. So how is insulin produced in the lab setting
so that those with Type 1 Diabetes will have an adequate amount of insulin to inject? Well one current and common way today is by
using bacteria in a lab. These bacteria in a lab can be given the human
gene for insulin and then the bacteria produce the insulin. Lots of benefits on that: bacteria are relatively
easy to grow, multiply quickly, don’t take up a ton of space. Both the jellyfish and insulin scenarios are
examples of transformation, which is the process where a cell – commonly bacteria - can take
up DNA from their environment and use that DNA. Transformation can occur in nature but these
transformations were specifically performed using genes of interest from other organisms. These two examples fall under the topic of
our video: genetic engineering. Genetic engineering can be very generally
defined as changing an organism’s genotype using biotechnology tools or techniques. Let’s focus more on the whole bacteria producing
insulin example to illustrate how this was done. Focusing first on some basics that we know:
here is a human cell. Like most cells in your body, it contains
a nucleus. And like most body cells, that nucleus contains
the organism’s entire DNA code. With some exceptions, each body cell you have
contains all of your DNA. If you recall, genes are made of DNA and so
there is a gene that codes for making the protein insulin in most of your body cells. While this gene could be removed from a cell’s
DNA, the gene for insulin can also be synthesized in a lab. This insulin gene can be inserted into a bacterial
plasmid. A plasmid is like an extra set of genes – in
addition to the bacterial chromosome - that bacteria can use. Plasmids tend to be in a circular shape. Plasmids are common in bacteria; you can also
find them in yeast cells. But to get specific DNA into the plasmid,
you have to make space for that. For that, you can use restriction enzymes. Restriction enzymes are enzymes that cut in
specific spots---like teeny tiny scissors---and can cut a specific spot in the plasmid so
you can add in that human insulin gene. Ligase ---you remember ligase from our DNA
replication video --- can be used to help seal it into place. This is now considered recombinant DNA because
it contains not only the plasmid DNA but also the DNA of interest, the gene for producing
insulin. The recombinant DNA is made up of DNA from
different sources. In order to encourage a bacterium to pick
up the plasmid in transformation, certain chemicals and temperature changes may be used. Once it picks up that plasmid, when the bacterium
reproduces by splitting, the resulting cells will both inherit the plasmid. And then their daughter cells will inherit
it. And theirs. You get the picture. In this way, the plasmid continues to be produced
over and over. The bacteria can use the human insulin gene
to produce human insulin and the insulin can be purified in a lab setting to be used for
humans. Let’s talk about some vocab in our example. In this example of genetic engineering, the
bacteria were genetically modified from recombinant DNA. You can consider the bacteria to be transgenic:
any organism or microorganism that has genetic material from some other organism is considered
transgenic. The plasmid was the vector in this situation. A vector can be thought of as the vehicle
for getting the recombinant DNA into the organism. Plasmids are a common vector. But plasmids aren’t the only vectors in
genetic engineering. Viruses are another example. If a virus’s own genetic material is removed
and a gene of interest instead is placed inside, the virus can then be permitted to attach
to target cells to deliver that gene of interest. When it attaches to a target cell, it inserts
the gene of interest. Viruses in this way are another delivery system. And viruses can target any kind of living
cell: bacteria, fungi, plants, animals – including humans. You can find examples with viruses in our
description. Sometimes if the plasmid or viral vector is
just not ideal for delivering DNA into a cell – well you have more options. There’s microinjection. A special kind of micropipette can inject
the gene of interest through the cytoplasm of a cell and into its nucleus. For example, if the target was a fertilized
mouse egg cell. Or- and I didn’t learn about this until
more recently - gene guns. Yes, really. A gene gun can shoot particles – gold particles
for example – that are coated with recombinant DNA. Really helpful in cases where you have thick
cell walls to get through, like a plant cell. Genetic engineering techniques and tools continue
to develop and change So when we were taking about restriction enzymes, and we mentioned
they cut in specific spots: they have certain sites they recognize and anytime that site
exists, they cut. Restriction enzymes are actually part of the
natural defense system bacteria have against bacteriophages; they can chop up bacteriophage
DNA. But what if you had a way to customize the
exact place you want to cut in DNA? Perhaps you’ve heard about CRISPR? This gene editing tool allows for the editing
of DNA using a special kind of nuclease called Cas9. Recall that nucleases, like restriction enzymes
and Cas9, can cut DNA and like restriction enzymes, the CRISPR-Cas9 system is also part
of the natural defense system bacteria have against bacteriophages. But in CRISPR, by using a specific guide RNA
that can be designed in the lab, the Cas9 can be guided with the specific guide RNA
to cut at points around a specific target gene. And by doing that, one can do gene editing
by removing a selected target gene –and if desired, a new gene could be inserted in
its place. CRISPR has been used in plants and animals
including clinical trials of humans. So now that we’ve covered some ways that
genetic engineering can be done, we want to address: how can genetic engineering be useful? There are tons and tons of examples of uses
for genetic engineering so just picking a few here: First, there’s use in the medical field. Producing insulin for those that cannot is
an example we mentioned and currently pharmaceutical companies also use genetic engineering to
make clotting factors, human growth hormone, and more. There’s genetic engineering in agriculture
– for example, genetically engineered crops that might better resist insect pests or herbicides
or drought. There’s genetic engineering research being
done for developing plants that could remove pollutants from the air or soil. And an example with animals? There’s work being done in genetic engineering
to develop chickens that are resistant to avian influenza, aka bird flu. Genetically engineered mice are often used
in research to better understand certain gene functions. However, with these examples we’ve outlined
and more, it’s important to mention there are also ethical considerations for genetic
engineering that must be examined and considered. Depending on the type of genetic engineering
being performed this could involve animal welfare or ecological concerns or equity in
access: again, those are just a few examples among many. We’ve included sources of bioethics involving
genetic engineering in our description. If the field of genetic engineering interests
you, just know that the career of a genetic engineer is a career that is expected to keep
on growing. Well, that’s it for the Amoeba Sisters,
and we remind you to stay curious.
