Genetics and the Basis of Biotechnology

Genetics and the Basis of Biotechnology

Many advocates of organic growing speak of genetic manipulation and bioengineering as unalloyed evil. In order to object we need to do so intelligently and reasonably, not with emotional objections. People may object to things emotionally when they don’t understand what something is or how it got there. To prevent that, here is a short lesson on the basis of biotechnology.

Plants are relatively easy to manipulate, which is why plant genetic engineering was possible decades before animal genetic engineering. As part of a plant’s ability to reproduce vegetatively (without seeds), specialized plant cells, such as root or leaf cells, can unspecialize, reproduce and then re-specialize. As a result, a scientist can induce plant tissue to unspecialize and reproduce. They can then take those cells and genetically modify them and get the cells to re-specialize, generating a new, genetically modified plant.

How Do They Do It?

There are two major methods of producing a genetically modified plant. The first method is essentially accelerated breeding. This is not fundamentally different than ordinary methods of selecting the biggest and best plants for future reproduction, just on the smaller scale possible in the lab. It’s faster than being able to breed the plants once a season.

It is the other technique of transplanting a gene from another species into a plant that most people object to. This is a technique that has no equivalent in nature, and this makes it much more dangerous.

The least technical way to genetically modify plants is to allow them to mutate on their own, and just screen for the desired mutations. The natural mutation rate is very low, and all living systems have advanced mechanisms in place to repair mutations. In order to get any significant number of mutations, the unspecialized cells are usually exposed to a mutagen. To obtain a herbicide resistant plant, for example, the most resistant plant is taken, and its cells are exposed to a mutagen. The most resistant is reproduced and exposed again. Eventually a plant can be obtained which has high resistance to the target herbicide, but without loss of other desirable characteristics like yield or insect resistance.

To transplant a gene from one species to another, two unrelated enzyme systems are exploited. The immune systems of both plants and animals include a series of enzymes that cut up DNA. This is a defense mechanism against viruses. Viruses which are not technically alive, but are a string of DNA inside a protein coat. When a virus attacks a cell, it injects its naked DNA into the cell, where the DNA tries to take over the cell’s mechanisms to reproduce itself. The cell’s defense is those DNA cutting enzymes that troll for foreign DNA, which they then cut up into little pieces to prevent it from taking over the cell. These enzymes are used in biotechnology to cut out specific genes from one organism to insert into another.

There is another type of virus called a retrovirus (like HIV, often associated with AIDS) which doesn’t immediately take over any cell it attacks, but integrates itself into its host’s DNA. It stays there for an indeterminate length of time, until it suddenly turns on its attack mechanism and starts attacking cells. The mechanism which these viruses use to integrate themselves into their host’s DNA, is used to integrate the gene from another organism into the DNA of the plant being manipulated.

Random Chance

Of course, this is not an easy or simple process. The place in the plant’s DNA where the gene is inserted is completely random. Plants and animals have millions of genes in their DNA, and only a few thousand of these genes are ever active at any given time. If the new gene is integrated into a portion of the plant’s DNA which is inactive, it will not be expressed.

A lab attempting to do this will have to insert the DNA into hundreds of plant cells and then test for the DNA inserted in an appropriate spot. They do this by attaching the new DNA to another gene called a marker. Most commonly, it is antibiotic-resistant because it is easy to test for. If the plant cell is resistant to an antibiotic treatment, the gene is being expressed. This brings its own problems though. There is some evidence now that eating foods with this introduced gene in it can destroy antibiotics in the gut. There is also the possibility that bacteria in the gut can pick up this gene, thus adding to the problem of superbugs.

Just because we can do something doesn’t mean we should. I’m disturbed that scientists and farmers are boldly introducing these organisms to the environment when we really have no idea what we are doing and there is very little testing.

We are like little children randomly mixing the chemicals under the sink; something useful might be made, or the whole house could blow up. There is no way to tell which it will be until it happens.

I encourage all people who are concerned to loudly object to the current applications of genetic technology. But do it intelligently and not emotionally; scientists are much more likely to respond to a rational argument.

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