Video Transcript
In this video, we’ll learn more
about how genetic technology has improved our health. We’ll discuss what a gene and
genome are and some of the things we’ve learned from the human genome project and
how we can use this information to improve our health. Then we’ll learn more about vitamin
A deficiency and how a special type of genetically modified rice called golden rice
can be used to get more vitamin A in the diet.
You may be sitting in a classroom
right now surrounded by other students. How related are you to one
another? Unless one of your family members
is in the class, you might say that you’re not very related. And in some ways, you’re not
wrong. You’re certainly more related to
your sibling than to a stranger. However, as humans, we’re all
related to some degree. It might surprise you to learn that
we all share about 99.9 percent of our DNA with one another. And with family members, we’re even
more closely related. So what does this mean exactly? And what does DNA have to do with
it?
Let’s review what DNA is for a
moment. If you take a microscope and zoom
in on your skin, you’ll see that it’s made up of cells. If we zoom in on one of these
cells, we can see that it contains a nucleus, which acts as a kind of command center
for the cell that gives it instructions to grow. Inside the nucleus is a special
molecule called deoxyribonucleic acid. This is a bit of a mouthful, so we
call it DNA for short.
There’s a lot of DNA inside human
cells. And if we were to take it all out
and line it up, it would be about two meters in length, which is probably even
taller than you are. The reason we can fit all of this
DNA into such a tiny nucleus is because the DNA is packed into structures called
chromosomes. You can see that DNA molecule here
after it’s unpacked from the chromosome. These colored boxes are called base
pairs and is the alphabet for the DNA code. This is how DNA can give different
instructions.
These base pairs are special
chemicals that we call guanine or G for short, cytosine, adenine, and thymine. There’s just four letters in the
alphabet for DNA, but the possibilities are endless. By putting these base pairs
together in different ways, we can create different characteristics. So if you have blue eyes, this kind
of characteristic in DNA can be represented by a certain sequence of base pairs,
maybe something like this.
We call the sequence of DNA base
pairs that gives certain characteristics genes. So in this example, this blue eye
gene gives the instructions for making the blue eye characteristic. This gene is a sequence of base
pairs on DNA. So the DNA sequence for this gene
might be located in the DNA as shown here. Some people have different-colored
eyes, so their eye color gene might be different or something like this. These two sequences are very
similar to each other, but there are some differences. There, now any differences are
circled in black. These differences are minor but can
be enough to have the blue eye or green eye characteristic.
Eye color is one example, but there
are many differences in the DNA of one person compared to another. But we’re still about 99.9 percent
the same as far as our DNA sequence goes. We know that we’re 99.9 percent the
same because we sequenced all the DNA in our cells. And we have a lot of DNA in our
cells. Remember if we took it all out,
unpacked it, and lined it up, it would be about two meters long. We call this complete set of DNA
the genome.
To sequence the genome, we needed
to start from the beginning and determine the sequence of all the base pairs all the
way to the end of our genome. This was a huge project that we
call the Human Genome Project. The Human Genome Project was a
massive worldwide collaboration between many scientists. It started in 1990 and was mostly
completed in 2003. In all, it cost about 2.7 billion
dollars.
After sequencing the human genome,
we discovered a lot of interesting things about it. The size of our genome is about
three billion base pairs long. That’s a lot of base pairs! Imagine you wanted to read the
sequence of the human genome. If it takes one second to read one
base pair, then it would take three billion seconds to read three billion base
pairs. How long do you think three billion
seconds is, one year, five years? It’s actually almost 100 years. That’s a huge amount of time!
We also found out that there’s
about 20,000 genes in the human genome. One of the shortest genes is about
800 base pairs long and is called the SRY gene. This gene is needed for the
development of the testes. And without it, there would be no
biological males. One of the longest genes is the DMD
gene. This makes an important protein in
muscle tissue. It’s made up of 2.4 million base
pairs and is about 0.08 percent of our entire genome.
The Human Genome Project has also
led us do genome comparisons with other organisms. This tells us more about our
evolutionary history. By doing this, we’ve determined
that our genome is 99 percent similar to the chimpanzee genome and is one of our
closest living relatives. You might be surprised to hear that
we also share a lot in common with mice. Our genome is 85 percent similar to
the mouse genome. And as we’ve mentioned, humans are
about 99.9 percent similar to one another. This 0.1 percent difference
represents about three million base pairs. So the difference between you and
me in terms of our DNA sequence is about three million base pairs.
These differences can help us in
medical research. By comparing the genome of someone
who is healthy to someone who has a disease, we can look for differences. These differences can help us learn
more about a disease so we can find cures. The Human Genome Project has given
us a way to learn more about ourselves and to fight disease.
By learning more about specific
genes in humans and other organisms, we can use them to our advantage. A good example of this is with
golden rice and how it can be used to treat vitamin A deficiency. People can develop health problems
if they don’t receive enough nutrients in their diet. A nutrient is something that we
need to survive and grow. These include carbohydrates, fats,
proteins, minerals, and vitamins. Vitamin A is important for the
growth and development of our bodies, especially in supporting the immune system and
for vision.
Vitamin A deficiency is when you
don’t receive enough vitamin A in your diet. This can cause blindness and a
weakened immune system, which can lead to death. This is most common in developing
parts of the world such as Africa and Southeast Asia. By getting more vitamin A in their
diet, this can save up to 2.7 million children from dying every year. In order to get enough vitamin A to
overcome this vitamin A deficiency, we actually need more of something else called
provitamin A.
Provitamin A is what we get in our
diet from the foods we eat. And once it’s inside of our body,
provitamin A is turned into vitamin A. So diets that get low amounts of
provitamin A will produce low amounts of vitamin A. And this will lead to vitamin A
deficiency. But for diets that get lots of
provitamin A, this will produce lots of vitamin A. And they will not be vitamin A
deficient.
So what food is one that is eaten
more than any other food in the world? Rice, although we may not recognize
it as a plant, it’s the grains that we cook and eat. Rice is a common food eaten all
around the world, and many countries rely on rice as a primary food source. Unfortunately, it contains no
provitamin A. So people who rely on rice as a
primary food source often don’t get enough provitamin A in their diet and become
vitamin A deficient. We can use a technique called
genetic modification to change or modify this rice plant so it makes provitamin
A.
Genetic modification is a technique
used to change the traits of an organism, like this rice plant, by inserting a gene
with that trait into the organism. There are several steps involved in
genetic modification. First, the gene for provitamin A
needs to be extracted from another organism that has the gene. This gene carries the instructions
for how to make provitamin A. Next, we have to modify the normal
rice plant, which doesn’t make provitamin A, by inserting the provitamin A gene. Now the genome of this plant has
the provitamin A gene and therefore has the instructions it needs to make provitamin
A. We call this modified rice plant
that includes the provitamin A gene golden rice.
When the rice plant has the
provitamin A gene, it makes a lot of provitamin A. It makes so much provitamin A, that
it actually changes the color of the rice grains from white to a golden color. This is why we call this kind of
rice golden rice. Now when people eat this rice as a
part of their diet, they’ll get a lot of provitamin A and will no longer be vitamin
A deficient. So what does it taste like? Apparently, it grows normally and
tastes just like normal rice, except it’s golden in color and a lot more
nutritious.
Besides golden rice, other plants
have been genetically modified too. Corn is a pretty tasty vegetable
for us as well as for insects like this caterpillar. Insects like to eat different parts
of the corn plant, and this could have an impact on the plant’s health. Special chemicals called pesticides
can be used to kill these insects and protect the plant. However, these have a negative
effect on the environment and on our health, so trying to limit their use is
important.
So instead, corn can be genetically
modified to carry a gene that makes it resistant to insects. This is because the corn plant now
carries an insect toxin that only affects insects and not people or other
animals. So when the insect goes to eat the
plant, it ingests this toxin and it dies. This way genetic modification of
the corn plant can reduce pesticide use, and this can be helpful for the environment
and for our health.
Another example is with
tomatoes. Tomatoes have soft skin and can
easily bruise when they’re transported. So we can genetically modify the
tomato plant so its skin is more tough and more resistant to bruising.
Genetic modification has many
benefits, but some people are worried about eating genetically modified food. This is because we’re eating things
that aren’t normally in plants, and this might cause an allergic reaction. There’s been a lot of research on
this, and the World Health Organization considers these foods safe to eat.
Now let’s try out a practice
question and apply what we’ve learned in this video.
The Human Genome Project found that
the genomes of humans are very similar. Roughly, what percent of the human
genome is shared between humans? (A) 80 percent, (B) 88 percent, (C)
greater than 99 percent, (D) 75 percent, or (E) 50 percent.
This question is asking us about
how similar our genomes are. So what is a genome exactly? Our body is made up of cells. Most of these cells contain a
nucleus that contains DNA. DNA is a special molecule that
gives the cells the instructions it needs to grow. It also gives us different traits
and is why some of us are taller and is why some of us have blue eyes, while others
have green eyes. These traits are given by sections
of DNA that we call genes.
If we unravel this DNA a little bit
and look at it more closely, we can see that there’s different sections of DNA that
we call genes that code for different traits. So this gene here might code for
the trait that makes this person tall, and this one here might code for the eye
color trait. If we unravel this DNA even
further, you’ll notice the double-helix-shaped structure and these different colored
boxes. These are called base pairs and are
special chemicals that are like a kind of alphabet. There’s guanine or G for short,
cytosine, adenine, and thymine. These base pairs give the
instructions needed for our different traits.
Here’s a short sequence of DNA,
which is made up of one, two, three, four, five, six base pairs. Different genes have different
lengths with unique sequences of these base pairs to code for specific traits. The Human Genome Project was a
worldwide project that aimed to determine the sequence of all the base pairs in
human DNA. A genome is the complete set of DNA
of an organism. In humans, the sequence of our
genome is about three billion base pairs long.
Once we had the complete sequence
of our DNA, we could then start comparing this sequence between humans. We found that our genomes were
about 99.9 percent the same. So even a stranger, who you are not
related to, shares more than 99 percent of their DNA with you. Therefore, more than 99 percent of
our genome is shared between humans.
Now let’s go over some of the key
points that we covered in this video. A gene is a section of DNA that
contains the information needed to produce a characteristic or a trait. The complete set of DNA inside an
organism is called the genome. The Human Genome Project was a
worldwide project that aimed to sequence the entire human genome. We found that the human genome is
about three billion base pairs long, contains about 20,000 genes, and that we all
share more than 99 percent of our DNA with each other. Finally, golden rice is a
genetically modified version of rice that can be used to help with vitamin A
deficiency.
