Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: thedoc on 20/01/2016 18:50:03
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Taylor Rowell asked the Naked Scientists:
My research topic is about the good side of GMO's having bug resistance in them. I would like to learn more about the resistance called bacillus thuringiensis. I would please ask if you could email me back if you have any information on this topic. Thank you for taking the time to read this email. I am in 7th grade and we are having debate.
What do you think?
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Here's the bad side of the good side!
Suppose I market a GM wheat that consistently produces say 20% more yield than any natural variety at no extra cost to the farmer. Now suppose you are a farmer. You have to sell your wheat in a market where your next-door neighbor is using my seed, so he can undercut your price by 20% every year. 20% is a big deal in this business, and the absolute consistency of my product means that he can afford to increase his acreage of wheat, knowing that he will get a good, cheap crop every year.
So eventually you will either go out of business, or have to use my cheaper, more reliable material. And the same will apply to every farmer in the area, and eventually in the world. The Good Thing is that there will always be enough wheat, at a consistent price, and everyone is happy.
Except that my GM wheat is sterile (because the anti-GM lobby insists that it must be!) so you can't re-seed from your own crop. Every farmer has to buy my seed or end up with an unreliable crop that he can't sell at a profit.
So within about 20 years, I have complete control of the world market for wheat. I can charge what I like for the seed, or even refuse to supply it altogether to countries that don't espouse Sharia law, or farmers whose name begins with R.
If you think this can't happen, look at the political influence of Saudi Arabian oil, or the world's economic dependence on Chinese manufacturing: a small but consistent price advantage can turn into a monopoly within a generation, and that is a Bad Thing, especially where food is concerned.
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Do GMO's have inbuilt resistance?
Some organisms like wheat and rice have been modified to be resistant to certain insects that might eat the crop.
But organisms can also be genetically modified for many other characteristics like faster growth, shorter stems (more resilient to strong winds), drought tolerance, herbicide resistance, to glow under ultraviolet light, etc. These changes would not protect them against insects.
For genes from this particular bacterium, see: http://en.wikipedia.org/wiki/Bacillus_thuringiensis#Use_of_Bt_genes_in_genetic_engineering_of_plants_for_pest_control
For general principles of GMO: http://en.wikipedia.org/wiki/Genetically_modified_crops
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Note that changes in a crop for improved yield in various climates can be made by conventional breeding techniques. This arranges cross-breeding of crop plants with related wild varieties found in different countries and climates. These wild varieties often have much lower food yields than the established crop plants. This takes a lot of work over very many years. The Green Revolution (http://en.wikipedia.org/wiki/Green_Revolution) (1930-1960s) improved food security in many poor countries in just this way.
Similar improvements in crop yields can also be made by genetic modification. This potentially could be done much more quickly, by moving just the desirable gene from the a wild variety into an existing high-yield variety. However, the regulatory approval adds many years to the process. Even if approved for sale, people may refuse to buy the crop.
There is an intermediate form of breeding which today would not be called genetically modified, but which takes advantage of modern gene sequencing techniques. Instead of waiting for a year or more to see which plants have taken up the desired gene, you can use gene sequencing to just focus on the plants which are expressing it.
But there are other types of genetic engineering, where genes from totally different organisms are mixed with a food plant, eg genes from a bacterium or a jellyfish. These cause the most concern among the public and regulators.
But the public and the regulatory process has trouble distinguishing genetic changes within a single species from those which are cross-species. So they all move extremely slowly.
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I wonder if, in asking this question, you are referring to the antibiotic resistance genes that are sometimes used to construct genetically modified organisms and are therefore carried, sometimes entirely and sometimes in part, by the final modified organism.
What I am referring to is a technique called positive selection. When genetically modifying an organism you need some method to select for the organisms that have been successfully modified or taken on the new trait you are seeking to confer upon them.
Let's take a bacterium as an example. Say I want to modify a bacterium so that it can produce insulin for me. If I just made a piece of DNA containing the insulin gene then there would be no benefit to the bacterium to make the insulin because bacteria don't use insulin, and making it would be a metabolic burden on the bugs. This would place them at a disadvantage so they would actually grow less well than unmodified bugs.
Instead, scientists would approach this problem by making a piece of DNA (usually called a plasmid) that contains both the insulin gene but also a gene that makes the bugs resistant to an antibiotic that would otherwise kill them.
Now, by adding the plasmid to the bacteria and then growing the bacteria in a solution of the antibiotic, only bacteria that have taken up the plasmid - and will be making insulin for me - will be able to grow, because they will also be making the antibiotic resistance gene.
So, sometimes scientists use antibiotic resistance genes to achieve "positive selection" for the trait they want to engineer into cells.