Wednesday, January 13, 2010

Benefits of Genetic Engineering

What are the benefits of genetic engineering? The benefits of genetic engineering are the products we can make with it. Genetic engineering could be used to make products in two ways: we could take the existing organisms and modify them genetically to make them more efficient. We could for example add a promoter that would make the organism produce more of one kind of protein. The second use of genetic engineering is that we can take new genes and insert them into organisms that never had them before.

The first major product of genetic engineering was human insulin. Insulin is a protein that acts as a hormone to stimulate uptake of blood sugar into tissues, such as the liver and the muscles. In diabetes, people don’t make insulin. Previously, insulin came from slaughtered animals. The insulin protein has 51 amino-acids. The insulin from slaughtered animals is similar to human insulin, but very often is one or two amino-acids different. It still has the same function, but the human immune system will recognize these one or two differences. So, in a significant number of diabetics, when taking non-human insulin, their immune system reacts against it.

Here, what we need is human insulin. Insulin is made in very small amounts. So, the only way to get this in reasonable amounts is by amplifying the expression of genes for insulin in recombinant DNA.

At City of Hope Medical Center in California, Keiichi Itakura went into the chemistry lab and made the insulin gene. It wasn’t even then a big deal to make it. Itakura’s colleague, Art Riggs, took this gene and put it into an expression vector, right next to a promoter. The expression vector now had the gene and a marker. The expression vector was then put into bacteria, and the bacteria expressed human insulin. This is about 7 or 8 years after the first emergence of recombinant DNA technology.

The insulin then was extracted, sent to a drug company, and then to physicians. This is the source of all insulin now used to treat type 1 diabetics. This is really the great example of a genetically engineered medication.

Another example is the blood-clotting protein that is missing in hemophilia. This blood-clotting protein can be supplied with genetic engineering. People no longer die of hemophilia thanks to genetic engineering. So, here we have two clear benefits of genetic engineering.

Proteins used to treat diseases


There is a protein called Erythropoietin (EPO). EPO is a hormone-like substance made by the kidneys. It enters the bloodstream, goes to the bone marrow and stimulates the production of red blood cells. Red blood cells only last about 120 days, so they must be constantly replaced. There are many people with kidney failure for various reasons. These people are treated with kidney dialysis, because kidney transplants are limited.

The kidney filters out the poisons and keeps the good things. In this case, all you can do is to filter the bad things with the dialysis machine. Among the things that get filtered out is EPO. So, these people with kidney failure have kidney function restored by dialysis, but they’re not making EPO. They have severe anemia. The only way to get around this is by massive transfusion or to treat them with EPO.

The gene coding for EPO was isolated, EPO was made by recombinant DNA technology, and this is now widely used for people who are undergoing kidney dialysis and also people who are being treated with cancer chemotherapy. Many of the drugs used in chemotherapy destroy bone marrow cells.

EPO is also the first genetically engineered drug of abuse. Athletes found that if they take some EPO they can increase their blood cell count. Increasing the amount of red blood cells by about 10% can give an athlete an edge in competition. There had been great controversies in cycling and elsewhere because of the abuse of EPO.

In Animals


Plants and animals can be genetically engineered to make products useful for us. The great example of this is diary animals. Sheep, goats and cows produce a lot of milk. Biologists found that the expression of genes for the major milk proteins is under the control of a promoter. This promoter is a sequence of DNA that causes the adjacent genes to be expressed in the mammary gland. It is called the lactoglobulin promoter.

This sets up a really nice opportunity for using genetic engineering. You could take the gene you want expressed in milk and put it into a DNA vector. Then you put this vector into a sheep egg cell. If you do this, the egg can then be developed in the laboratory for a couple of days until it becomes an embryo. You can insert the embryo into a mother and the offspring that are born are sheep that would make milk which contains this extra protein. This was actually behind the reason for cloning Dolly the sheep.

There are a significant number of humans that lack adequate amounts of growth hormone. These people are very short in stature. The growth hormone is a protein. So, we can get that protein from the body, but it is made in the pituitary gland in extremely small amounts. So, again, we got to get it through genetic engineering. The gene was isolated, put into a vector, put into cows, and there is a herd in Argentina of ten cows that in their milk will supply the world need for human growth hormone every year. This process is called pharming, and a very promising technology.

In Plants


Plants can be genetically engineered to make useful products. Genetically engineering a plant is a lot easier than animals. We don’t need to inject and expression vector into the fertilized egg of a plant, because plant cells are totipotent. We can take any plant cell grown in a laboratory, put the vector in, and then grow the plant up from that cell.

Plants produce a lot of protein. For example, tobacco plants have been genetically modified to make TPA in their leaves. Tobacco leaves are very large and it is easy to get the TPA from them.

You’ve probably heard the term antibody. Antibodies are what the immune system makes to fight diseases. A “plantibody” is a plant is making a human antibody. We can use genetic engineering to have a plant make a vaccine. For example, the vaccine against bacterial meningitis has been expressed in the fruit of plant, a banana plant. The people still have to eat the fruit, but it doesn’t have to be refrigerated and you don’t need health professionals to administer it.

We can create plants with new capabilities. For example, a major component of detergents is lauric acid. This molecule is made in a biochemical pathway in tropical plants, such as coconuts and palm trees. A major source of it is palm kernel oil. Scientists pinpointed one of the key enzymes that is in the biochemical pathway for making lauric acid. Scientists pinpointed the gene in palm trees, they cloned the gene into an expression vector and put it vector into rapeseed plant that produces canola. Normal canola produces oil that is 0% lauric acid. This particular transgenic canola makes 60% lauric acid.

There is a viral disease caused by the tobacco mosaic virus. This is a major pest of tobacco. It doesn’t kill the plant, it kinds of destroys leaf tissues and spreads very rapidly. This virus reproduces in the cells but doesn’t kill the entire plant. The viral genome can be replaced with other genes; in this case, with genes for vaccines. Now, instead of making a lot of proteins in viral particles, these tobacco plants are making large amounts of a vaccine. This may be a new use for what is widely grown crop around the world.

These are just a few benefits of genetic engineering. I’m sure more are coming in the future, as we discover more and more about genes and proteins.

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1 Comment:

JordanT said...

In the first paragraph of in animals it says in DIARY animals not DAIRY.

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