Lesson Video: Genetic Engineering Biology

In this video, we will learn how to describe the process of genetic engineering, and discuss its positive and negative implications.


Video Transcript

In this video, we’ll learn what genetic engineering means and why it’s important, how some enzymes are actually used to cut and paste DNA between organisms of different species, take a look at a few examples applications of this technology, and work a practice problem or two. By the end, we’ll have a basic understanding of how genetic engineering can be used to solve problems involving life.

Let’s start with a basic overview of genetic engineering. Well, a gene is a section of DNA that codes for a protein generally and can affect one or more traits. And the verb form of engineer means to design or build. And in the case of genetic engineering, what generally occurs is really more of a partial rebuild. So genetic engineering has to do with a partial rebuilding of the genome or genetic information of an organism. But let’s look a little bit deeper. Thousands of years ago, humans realized they could change or modify the traits of plants or animals by selecting the organisms with the traits that they really liked for breeding. This is called selective breeding.

Over one or more generations, particular traits can be adjusted, such as flower size as long as the trait has a genetic basis or, in other words, that the trait is coded for by a gene in the organism’s DNA. But in the 1970s, biologists developed a technique referred to as genetic engineering that specifically alters an organism’s DNA by transferring a gene of choice from one species to another. A common example of this technique uses a gene from a jellyfish that produces a glow in the dark protein. This gene has been transferred into several other species, including cats, pigs, and zebrafish.

Making a cat glow is great, since they do seem to enjoy tripping people, and glowing makes them hard to miss, even in the dark. But let’s take a look at some other reasons why genetic engineering has become increasingly common over the past 50 years. Genetic engineering has many practical applications. In the medical field, it’s used for gene therapy to produce therapeutic proteins like insulin or antibodies and in medical research. In agriculture, genetic engineering has been used to improve crop yields, nutritional content, and resilience to pests, pathogens, herbicides, and environmental change. In addition, growth rates have been increased in some animals that are farmed, such a salmon.

Some industries also use genetic engineering to produce proteins quickly, cheaply, and with less environmental damage for medical applications, food production, and more. Genetic engineering is also highly valuable tool in biological research as scientists continue to unravel the mysteries of life. Let’s review some concepts of DNA structure, the base pairing rules for DNA, and the genetic code before moving on to how genes are moved between species.

Let’s take a look at the structure of DNA first. The shape of DNA is a double helix, which resembles a twisted ladder. But in this diagram, the twist has been removed, so we can see the parts more easily. DNA contains deoxyribose sugars, phosphate groups, and four different types of bases that include adenine, thymine, cytosine, and guanine. When a DNA molecule is assembled, small groups called nucleotides that contain a sugar, a phosphate, and a base bond together to produce the DNA polymer. Nucleotides bond from one base to another, forming base pairs that can either be from adenine to thymine, or A to T, or cytosine to guanine, C to G. And these are called the base pairing roles.

Genes are located along the length of DNA molecules and are also a lot longer than indicated in our diagram here. The average length of a human gene is over 8000 base pairs long. The nucleotide sequence in genes encodes instructions for the order of amino acids and proteins. So if you move a gene from one organism to another, it enables the organism that receives the gene to make that particular protein, since the genetic code of DNA is virtually the same in all species. In the eukaryotic cells of animals, plants, fungi, and protist, DNA is long and linear and coils into structures called chromosomes, while the prokaryotic cells of bacteria and archaea contain DNA like our own but circular. And they can have smaller DNA molecules called plasmids as well.

And viruses, which can be used in genetic engineering, are generally considered not alive, but they do have either DNA or its nucleic acid cousin, RNA. Next, we’ll take a look at how restriction enzymes can be used in genetic engineering. Next, we’ll take a look at how restriction enzymes can be used in genetic engineering. Our goal is to produce the protein hormone insulin, which is a medicine used to treat diabetes. And we wanna produce that insulin from a population of bacteria. Does a bacterium need to regulate sugar in its blood? Of course, not. Organisms as small as bacteria don’t need huge circulatory systems filled with blood. So it doesn’t need and doesn’t produce the hormone insulin either.

So we need to get the human insulin gene from a human cell, and then we need something that can carry this gene once it’s removed from the rest of the DNA around it. The vector is used to carry this gene into its new home in a bacterial cell. And one commonly used vector is a plasmid, the small circular DNA molecule that’s normally found in prokaryotes and even a few eukaryotes. And we need a particular restriction enzyme represented here by a pair of scissors that binds at a certain sequence of base pairs called a restriction site.

You may remember that enzymes are usually proteins, and they catalyze or speed up chemical reactions. Well, the reaction that these enzymes speed up is the breaking of specific bonds on DNA molecules. The restriction enzyme in the diagram makes the cut represented by the black dashed line, resulting in a staggered cut that leaves sticky ends, sticky because they can stick back together again, or to another piece of DNA that’s cut with the same restriction enzyme, because it, too, will have the same complementary sticky ends.

So what other DNA should we cut with the same restriction enzyme. So where should we have the restriction enzyme make these cuts? Here’s a hint. There should be three. We’ll definitely need a cut on either side of the insulin gene to isolate it from the rest of the DNA that it’s attached to and another cut on the plasmid to make an opening where the insulin gene could be inserted. Now the plasmid in the diagram is a little larger, so we can see how the sticky ends of the insulin gene align with those of the plasmid forming the complementary base pairs of adenine and thymine and cytosine and guanine, which are held together by hydrogen bonds.

Before a vector is ready to transport the gene, it needs to reform the bonds between the sugars and the phosphates that were broken by the restriction enzymes. And the enzyme needed for this reaction is gonna be called DNA ligase. And now the plasmid could be moved into a bacterium using a process called transformation. As bacteria containing the plasmid reproduce by dividing in two, they also produce copies of the plasmid. Bacteria can be grown in conditions to promote population growth. And since each bacterium is gonna be genetically identical to the others, this process is known as cloning. And we’ve reached our goal. We have a population of bacteria that have the insulin gene, and they could be used to produce the hormone insulin.

There are other really great reasons to modify the genes of organisms, like these insulin-producing bacteria. But there are disadvantages as well. Let’s take a look at some of these. First, genetically modified organisms or GMOs have been engineered to contain DNA from another organism, like bacteria that contain the human insulin gene. We’ve already listed some general advantages of genetic engineering when we discussed reasons to use this technology. So we’ll discuss some more specific advantages of genetically modified organisms here. Microorganisms like bacteria are relatively cheap to grow, especially compared to animals. They reproduce quickly and can be engineered to produce hormones, enzymes, antibiotics, or to consume pollutants such as oil.

Even plants and animals can be modified to produce disease-fighting proteins like antibodies and antigens that can be extracted from either their plant tissues or milk or eggs. As the human population grows, but available farmland does not, genetically modified organisms will be able to help increase crop yields and nutritional content of certain foods. And this will increase food security for our future. Plenty of other advantages of GMOs exist, but let’s turn now to looking at a few of the disadvantages.

Many of the concerns around GMOs are centered around the fact that we just can’t know all the possible risks. There are a lot of unknowns. Another concern is that antibiotic resistance genes used in genetically modified bacteria may potentially transfer to pathogenic or disease-causing bacterial species, making that disease very hard to treat. All life forms get mutations; even viruses get mutations and so will GMOs. And that leads to greater uncertainty in the outcomes. There’s also concern that this technology will be used to make humans there faster, stronger, and smarter, a whole new elite class of humans. What will that do to society?

There is concern that people with the wrong intentions will use this technology for unethical purposes. Many farmers depend on a few huge corporations to supply them with genetically modified seeds that are patented. And this leads to some concerns about our food security. There’s a lot more to the ongoing debate regarding GMOs, but it seems certain that they’re here to stay. And we need to stay informed to make sure that they’re used wisely. Next up, let’s apply what we’ve learned to a practice problem.

Which of the following best defines genetic engineering? (A) Genetic engineering is the repeated breeding of organisms with desired characteristics. (B) Genetic engineering is the modification of the DNA of an organism. (C) Genetic engineering is the modification of the physical characteristics of an organism. (D) Genetic engineering is a form of cloning. (E) Genetic engineering is the creation of new animals.

Key knowledge required to answer this question is a basic understanding of genetic engineering. So let’s take a look at an example of this technique. Have you ever had to go to the doctor to get a vaccination and they take out a great big needle? Well, it’s possible that maybe someday we’ll be getting vaccines from bananas. Vaccines are an important tool to prevent disease, but they often come with a painful shot. Would you like it if you went to the doctor and they said, for your vaccination this year, you just have to eat this banana?

Genetic engineers have been working on making edible vaccines, and this is the basic gist of what they’re doing. They need to start with something edible, like a banana, and the pathogen, which is the disease-causing agent. And they have little proteins on them that our immune system can recognize to attack, and those little proteins are called antigens. After locating the gene that codes for the antigen and the genetic material of the pathogen, this gene is isolated from the rest of the pathogens’ DNA, and it’s inserted into the DNA of the banana. But since bananas are just part of a banana tree and banana trees have many, many cells that contain DNA, this process is just performed on a few banana tree cells. Then the cells are cultured and grown.

Now the bananas will have the antigen from the pathogen grown in them. And the idea is if you eat enough of the antigen, your immune system can recognize it and get all ready in case the real virus or bacterium or other kind of pathogen shows up. So this banana, like all genetically engineered organisms, contains DNA from more than one kind of organism. So that’s what genetic engineering is.

And it’s time to look at our solution options, starting with (A), genetic engineering is the repeated breeding of organisms with desired characteristics. But that’s selective breeding and humans have been doing that for thousands of years. It’s not really considered genetic engineering. Option (B) says, the genetic engineering is the modification of the DNA of an organism. And that’s exactly what happened in our example. So this one sounds really good. Option (C) says, the genetic engineering is the modification of the physical characteristics of an organism. Well, genetic engineering does modify physical characteristics of an organism, but not directly. You have to modify the DNA to result in a change in physical characteristics. So option (C) is not correct.

Option (D) says that genetic engineering is a form of cloning. Well, cloning is really a part of the process in genetic engineering. After you have the cell genetically modified the way you want it, you clone it or make lots of identical cells. So option (D) is not correct. Option (E) says that genetic engineering is the creation of new animals. But genetic engineering is really about moving a gene of interest from one species to another species. So option (E) is not correct. Therefore, the answer to the question, which of the following best defines genetic engineering, is genetic engineering is the modification of the DNA of an organism.

Here are a few key points from our lesson on genetic engineering, including a little summary diagram of how to use restriction enzymes to make blue tomatoes.

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