Genetic engineering vs. selective breeding. Are we all talking about the same? (by Diego Fdez-Sevilla PhD)
It is a subject of shared interest that I believe needs to be understood from the bases. I am aware of that any opinion expressed is subject to bias so my only intention is to gather information about GMO and Non-GMO.
My intention in this post is just to begin from the bottom up. I have been in conversations where some parts (scientist among them) defended that it is the same Genetic engineering and selective breeding. And that is why I have come to decide to bring forward a very simple matter which it seems not to be so clear after all: are we all talking about the same?
In one of the three links that I posted at the bottom (“Genetic engineering vs. selective breeding” What’s the difference?) Craig Holdrege, director of The Nature Institute, explains that the most critical difference between natural and GM breeding is that natural breeding crosses only organisms that are already closely related—two varieties of corn, for example—whereas, in contrast, GM breeding slaps together genes from up to 15 wildly different sources. Here’s how he explained the convoluted GM breeding process:
To make a GM plant, scientists need to isolate DNA from different organisms—bacteria, viruses, plants, and sometimes animals (or humans if the target gene is a human gene). They then recombine these genes biochemically in the lab to make a “gene construct,” which can consist of DNA from five to fifteen different sources. This gene construct is cloned in bacteria to make lots of copies, which are then isolated. Next, the copies are shot into embryonic plant tissue (microprojectile bombardment), or moved into plant tissue via a particular bacterium (Agrobacterium) that acts as a vector. After getting the construct copies into the embryonic plant tissue, whole plants are regenerated. Only a few plants out of many hundreds will turn out to grow normally and exhibit the desired trait—such as herbicide resistance.
Joe Mendelson, director of the Center for Food Safety:
The difference is pretty large. In regular cross pollination, the species being crossed have to be related . . . basically respecting their common evolutionary origin. But with GMOs, you can take any gene from any species and splice it into a crop. So you get fish genes in tomatoes or the like.
My take on this.
I have been looking for answers into a question which is out of my league as I am not a specialist in genetics. As biologist, I have studied that the metabolism of a given organism is fine-tuned through co-regulation of genes. So, I look into Genetic engineering (right or wrong), and the introduction of forced expression of foreign genes into already settled metabolisms similarly as, if when modifying the engine in a car to deliver more power is going to create a more demanding performance for the brakes, cooling system, battery supply, petrol consumption, etc… for which they have not been originally designed to. And this thought creates my question:
How the expressions of unfamiliar genes (genes that are from unrelated organisms) interact with the performance of the metabolic pathways in the host organism? If the expression of the “new incorporated genes” is a priority by “engineering design”, the energy and resources needed to supply this demand (Carbon chains, etc) would compete with the metabolic pathways designed originally to accomplish the demands of the host organism. Am I in a wrong direction here?
Recently I have found an article which is related with this matter:
In this study, genetic manipulation of a key enzyme responsible for controlling availability of single carbon units dramatically altered the expression of genes that control the composition of plant compounds called alkaloids. The results suggest that alkaloids serve as a source of one-carbon units when metabolic demand is high. This is an example of how metabolism is fine-tuned through co-regulation of genes that appear to be unrelated based on our previous understanding.
For further reading I suggest also these three links:
- – Genetic engineering vs. selective breeding What’s the difference?
- And this article (bit long) with a, I believe, nice discussion on the subject at the end http://www.bostonreview.net/forum/pamela-ronald-gmo-food#comment-3897
I want to leave also here an article which does not resolve my question but makes (I believe) a good background to see what are we dealing with “A new process for domesticating animals and plants, the Genetically Modified Organisms” including “Gene transfer between organisms of the different kingdoms”.
final quote: “in principle, it will never be possible to predict exactly what will be the concrete outcome of a given genetic program. Of course when things are kept very similar to one another they must more or less behave in the same way, but very minute differences, such as those that separate dogs from wolves, can have enormous consequences . We should always bear this in mind when considering our practices involving living organisms.”
Here I have found a paper addressing partially what I am looking for. The paper addresses “the effect of the resistance gene on fitness“. For those interested in this line of research I would suggest to look for articles citing this one as a start.
Fitness Consequences of Genetically Engineered Herbicide and Antibiotic Resistance in Arabidopsis thuliana. Colin B. Purrington and Joy Bergelson. Copyright 0 1997 by the Genetics Society of America.
“The current experiment measures the effect of the resistance gene on fitness while simultaneously controlling for possible linkage, the effects of the vector plasmid, insertion position, and induced mutation.”
“We obtained opposite results for the two resistance traits that we engineered into A. thaliana; expression of antibiotic resistance had no detectable consequence while herbicide resistance caused large reductions in fitness. The cost of herbicide resistance is a convincing demonstration that the addition of a single resistance gene can have an effect in plants similar to that observed in bacterial systems.”
I am still puzzled about if there would be any side effect in the metabolic process from forcing foreign/unrelated gene expression. The molecular weight and energy consumption needed to develop, not only a protein from a different natural kingdom, but also the mechanism to get it introduced in the rest of the organism structure, transport, and general sustainability… I would like to have more research about it since potential harms to human health have been claimed by the World Health Organization as including direct health effects (toxicity), tendencies to provoke allergic reaction (allergenicity), specific components with toxic properties, the stability of the inserted gene, nutritional impact and unintended effects that could result from genetic modification.