Introduction to genetic engineering | Molecular genetics | High school biology | Khan Academy

The idea of genetic engineering is something that we associate with the 20th century. We didn't even know that genes were actually the mechanism of heredity until the middle of the 20th century, and the direct modification of genes for some purpose really didn't even start happening until the 1970s.

But it's worth noting that human beings have been, in some ways, influencing the genetics of organisms for a very, very, very long time. For example, in nature, you have things that look like this; we call them wolves. But today, in our lives, we also have things that look like this. Now, these dogs did not come about naturally; they came about from many generations of breeding.

Human beings took things that started off looking like wolves or foxes and selected for certain traits. They might have selected for traits that made them smaller and made them look more like puppies, even when they were full grown, or traits that made them more docile, so they were more likely to listen to what a human being says to do, or traits that made them good at killing rodents or whatever else it might be.

Over time, repeated selection of those traits led to what we see as these different breeds of dogs. So, even though human beings were doing this for hundreds and thousands of years, they were influencing what DNA gets passed on from one generation to another. They didn't know about the actual genetic code, but it was a form of genetic manipulation nonetheless.

Similarly, if you look into the plant kingdom, when you go to the store and you see that sweet apple, things like that might not have existed in the form that you see them today. It is very likely—in fact, most agricultural products—people might have found wild apples, and we could be talking thousands of years ago. They might have found wild apple trees.

Let me draw a quick apple tree here. They might have found that the apples were a little bit sour and small and hard to eat and hard to digest. But over time, people selected the trees that had sweeter apples, that had larger apples, and made the conditions so that they were more likely to reproduce.

So, over time, you got larger and sweeter apples, like the type that you see at your store. As I mentioned, most agricultural products that we have today are the result of hundreds or thousands of years of this type of breeding. So, even though that might not be the formal definition of genetic engineering—which typically refers to something like gene modification, which we've only been able to do in the last few decades—human beings have been doing some type of influence on organisms' DNA for a very, very long time.

But with that said, in the last few decades, we've been able to become much more precise with influencing DNA through genetic engineering. In other videos, we'll go into more detail about how that is done, but you have this idea of recombinant DNA, where you could take genes from one organism and put them in another organism.

You might say, why is this useful? Well, let's say that there is a tree you want to grow. Let's say it's an apple tree, but it's very susceptible to a certain type of disease. If that disease hits, you lose all of your crop. But what if you could insert into the DNA of that apple tree maybe a gene that makes it more resistant to that disease?

And this is what people actually do today. They will insert DNA and it could be from pretty wild things. I've read stories about inserting insect DNA into a plant so that it will be more robust in some way or another. Now, this idea of recombinant DNA and genetically modifying food is often known as a genetically modified organism.

This is somewhat controversial. Many people say, hey, this is good; it allows us to produce more robust foods. In fact, part of this recombinant DNA inserting DNA into something else might make it more nutritious; it might provide for more vitamins. But other people would argue that, hey, we don't know exactly what all the repercussions of what we're doing will happen.

We might think it's helpful, but when you're taking DNA from one organism and putting it into another, how does that affect the nutrition or the long-lasting effects of eating that over time? So, this is something for you to think about.

And we're starting to go—when we start asking these questions—into the field of bioethics. As we have more and more control over the genome, and especially, as we'll see, the human genome, there's questions that we have to ask about— is it good or is it bad?

But going back to this idea of genetic engineering and recombinant DNA, other things that you could do is you could—let's say that we need to produce insulin for diabetics. Well, maybe you can take a bacteria cell and insert into the bacteria cell the gene that helps produce insulin. Then all of a sudden, that bacteria cell can become a human insulin-producing factory. So that we can have more insulin for diabetics; this insulin could then be harvested.

That is a use of recombinant DNA. So we really are going into an interesting period in humanity. For many thousands of years, we were breeding things, but now we're learning to manipulate things at a very fine grain level, and it makes us ask all sorts of questions.

There are likely to be some very good things we can do—produce new medicines, produce more robust crops—but there are also questions about what are the side effects. And the bioethics get really interesting when we start thinking about modifying the human genome itself.

Because when you're modifying genetics, you're not just modifying one organism; you're modifying all of their offspring. You're modifying the genes that exist in the gene pool. And so, some very good arguments for modifying the human genome are correcting diseases—some things that could be very serious.

But over time, things might—people might say, hey, I want to be a little bit taller, or I want a certain hair color, I want straighter teeth, or they might say, I want a child who has this trait or that trait. So things get very, very interesting the more we think about how genetic engineering may be used.