Video Transcript
Which of the following would not be
an example of an organism modified by genetic engineering? (A) Soybeans have been made to
express an enzyme that helps them develop a tolerance to herbicides. (B) A species of corn has had the
gene for an insect toxin inserted into its DNA, meaning it has developed some pest
resistance. (C) Seedless grapes are sprayed
with solutions containing the hormone gibberellin to increase their size. Or (D) a species of tomato has the
gene for a specialized salt pump inserted into its DNA, meaning it can grow in very
salty soil.
This question is asking us about
genetic engineering. So what is that exactly? Let’s clear the answer choices so
we have more room to work with. Genetic engineering is the
artificial manipulation of an organism’s DNA, usually to produce certain traits that
are beneficial. A good example is how bacteria can
be genetically engineered to produce the hormone insulin. Insulin is a hormone that controls
blood sugar levels. It can do this by signaling to a
cell to take up glucose. This glucose can then be converted
into energy in the cell and is needed for the cell’s physiology. In the disease diabetes, insulin
isn’t produced at sufficient levels, so glucose isn’t taken up and the cell’s energy
levels decrease. Without enough energy, the cell
can’t perform its functions as effectively.
So in diabetics, insulin needs to
be provided as a medication. Insulin is mostly prepared by using
genetically modified bacteria. These bacteria have the gene for
human insulin inserted into a special piece of bacterial DNA called a plasmid. This can then be transferred into
the bacteria. Inside the bacterial cell, the gene
for human insulin can be expressed to give rise to the insulin protein. This can then be extracted and used
for treatment of diabetes. So in this example, the bacteria
have been genetically modified to include the gene for insulin. Now let’s bring the answer choices
back and go through them to see which one of them is not an example of genetic
engineering.
In the answer choice that states
soybeans have been made to express an enzyme that helps them develop a tolerance to
herbicides, the fact that they’ve been made to express an enzyme implies that the
genetics of the soybean have been artificially manipulated to carry the gene for
this enzyme so it can be expressed. So this is an example of genetic
engineering. This means that this answer choice
is incorrect. In the answer choice that states a
species of corn has had the gene for an insect toxin inserted into its DNA, meaning
it has developed some pest resistance, the fact that this gene has been inserted
into the DNA of the species of corn is artificial manipulation of this organism’s
DNA and is an example of genetic engineering. Therefore, this answer choice is
also incorrect.
In the answer choice that states
seedless grapes are sprayed with solutions containing the hormone gibberellin to
increase their size, there is no indication of genetic engineering because that
organism’s DNA is not manipulated in any way. A solution containing a hormone is
simply applied, which is what is causing the increase in grape size. So this is not an example of
genetic engineering, which is what this question is asking us and is therefore
correct.
But before we finish, let’s look at
the final answer choice just in case. In the answer choice that states a
species of tomato has the gene for a specialized salt pump inserted into its DNA,
meaning it can grow in very salty soil, here the gene for a salt pump is inserted
into the DNA of the tomato, which is artificial manipulation of the organism’s
DNA. So this is an example of genetic
engineering, and this answer is incorrect.
