GLP Infographic: How crops are modified–Are GMOs more dangerous?

Why do scientists say that genetic engineering of crops is just the “latest chapter” in 10,000 years of high-tech agriculture? Or that genetic engineering is just a more precise way to breed plants compared to conventional breeding? Plants swap genes even without the help of human beings when they reproduce sexually, and our ancestors guided the process to develop crops suitable for agriculture. This GLP infographic presents four main ways in which crops have been genetically modified by humans: traditional breeding, mutagenesis, RNA interference and transgenics.

(Click to view high resolution image)


Traditional breeding of crops existed since the beginning of human civilization. Today, it encompasses a whole range of techniques, including high-tech ones like marker-assisted breeding. In traditional breeding, lots of genes are swapped at once, a process that can be “messy,” as described by Cornell plant breeder Margaret Smith. While breeders have been able to cross plants with their wild relatives (called a wide cross) to produce hybrids, the possibilities of using genes from distantly-related or other species are limited.

In the 1920s and 1930s, scientists explored the effect of radiation on a wide variety of plants. They found that applications of radiation produced mutations in plant genomes, creating plants that were different from the original. The Rio Star grapefruit was developed when Texas scientist Richard Hensz irradiated Ruby Red grapefruit seeds with X-rays. The new grapefruit had darker flesh and greater resistance to cold, which helped it survive a severe freeze in 1983 that killed other grapefruit trees. Since the 1940s, thousands of other crops have been produced with mutagenesis.

As molecular techniques in biology became available around the 1970s, scientists began to look more precisely at ways to alter genes in plants. RNA interference techniques allow scientists to switch off genes coding for undesired traits precisely, while recombinant DNA techniques allow them to insert genes coding for desired traits precisely. Other than allowing more precision in genetic modification, these molecular techniques also open up the possibilities of using genes from other species.

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10 thoughts on “GLP Infographic: How crops are modified–Are GMOs more dangerous?”

  1. Jon, what you are calling RNA interference bothers me.

    The term is an accurate description of the technique, but it involves inserting a gene to create the RNA that does the silencing. Therefore it suffers almost identical hostility from the anti-GMO crowd.

    What bothers me is that there is a different technique for silencing genes, using RNAi, which doesn’t involve any gene changes at all, and that this is likely to be confusing to people.

    • Charles, thanks for pointing that. We realized that and some other issues–RNAi is actually transgenics, and to some transgenices implies cross species gene insertions and to others just ‘novel’ genes. Also, creating categories implies differences, which is problematic. We made choices, believing that this could serve as a rhetorical tool to help discuss some myths surrounding the controversy.

      • Jon, I’m not sure we are there yet. There’s some work about RNAi, in which the genome of the “target species” is not changed at all. The idea is that some RNA originating in one species (or in a lab) can get into the cells of another species and control its DNA expression. It is possible that this happens in nature – there was a research paper by some Chinese researchers about RNAi from rice getting into the blood streams of animals who ate the rice. GMO critic Jack Heinemann has raised the specific fear that a GMO wheat might have a gene similar enough to a human gene that short stretches of messenger RNA from the wheat could silence that human gene for people who consumed the wheat. I’ve also seen the suggestion that short stretches of RNA produced by plants could get in to the cells of pest insects and cause their death.

        I don’t think I understand this well enough (yet) but it has found its way into discussions of GMOs and other ways of using biotechnology in agriculture.

        • Charles, not sure what you mean when you say “we are not there yet.” Some uses of it are quite clear and exact, such as the creation of the Arctic Apple. The Chinese study was less than meets the eye in my mind. I wrote about it here: . It’s hard to take any speculation by Heinemann seriously. Yes, there is more to learn but not much it appears as to potential dangers based on what we know now.

          • Here’s my concern maybe expressed more clearly. Look at this reference:


            It is about a proposed method of controlling an insect, which is the vector of a plant disease, by getting a bit of RNA into the insect’s cells which will interfere with the DNA-mRNA-protein pathway for a particular gene that’s important to the insect. In this case the RNA would be gotten into the insect using a virus. The insect genome is not changed. The orange genome is not changed. In effect, the RNAi is a kind of highly specific pesticide – never mind how it is delivered.

            This is a fundamentally different technique from the trick used for Arctic apples, in which the apple genome is changed by including an antisense DNA to silence the unwanted apple gene.

            I know that the Zhang paper may well have reported only an honest experimental error. It did, however, lead to speculation about how RNAi could possibly be used to control the gene expression in a target organism without changing its genome.

            I would be the last person to give Heinemann any credibility, but his scare story was widely circulated in the anti-GMO community. Like it or not, the term RNAi is out there to help confuse people.

            It would not be helpful to mix up the term RNAi in the sense of the huangbinglong control technique with the antisense RNAi technique.

  2. So basically for scientists to unzip DNA they take substances from bacteria and viruses and combine them with substances that have known DNA from other animals? I’m asking because despite all the info I’m looking at I’m still unclear about how scientists are creating GMO’s. I just trying to understand are harmful chemicals used in developing GMO’s and if so does that effect consuming genetically altered food? Or are there other factors that make everyone afraid of GMO foods?

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