Experimental evidence shows that New Genetic Engineering processes unintentionally cause genetic changes that are unlikely to result from conventional breeding. The site of the genetic changes as well as the resulting gene combination can be specific to the NGT processes.
An example: scientists in China altered the genome of rice using CRISPR/Cas gene scissors to induce smaller growth but increased yield. The focus of these particular experiments was, however, not on the intended altered characteristics of the rice plants, but on the unintended changes in the genome caused by the gene scissors. The investigation showed that the intervention into the rice genome was far from precise.
So-called off-target effects were found in DNA regions that were very similar to the actual target sequence. This is because the genetic scissors can confuse these off-target regions with the target sequence and unintentionally cut at these sites. The scientists used PCR methods to specifically check for such off-target regions in the CRISPR rice. These investigations revealed off-target changes in some of the plants.
In addition, some very different changes were found when the target sequences in various CRISPR rice plants were examined. Basically, most of the modifications mediate the desired effect, i. e. the target gene is knocked out. However, it can also happen that the DNA change causes the formation of new, undesirable gene products. In one rice variety, the target sequence was altered in such a way that a novel, truncated protein was unintentionally formed. Large, unintended restructuring of the target region was also found, which has already been described several times in regard to human and animal cells.
A further source of error was linked to unintentional genetic changes: before the genetic scissors can cut, they must first be introduced into the cells. In the case of plants, this is often done using older, non-targeted genetic engineering methods. As a result, the process causes additional genes to be unintentionally inserted into the plant genome. Such DNA fragments were also found in the CRISPR rice.
This example shows: if genetic engineering methods are used for important agricultural plants, all resulting organisms must be thoroughly examined for unintended genetic changes. If these are overlooked, they may rapidly spread throughout larger populations.