Hornless GE cattle

Gene scissor errors only discovered years later

The use of gene scissors is not as uncomplicated as often suggested. A part of the problem: the gene scissors have to be inserted into the cell before they can be activated. In a first step, the DNA for the gene scissors is usually introduced into the cells of plants and animals, often by using additional tools such as genes from bacteria. Indeed, the processes of New GE involve several technical steps that are associated with risks, no matter which traits are intended. These processes frequently result in additional genes being unintentionally inserted into the genomes of the plants and animals.

Errors made when using gene scissors can be easily overlooked if the actual complexity of the procedures is disregarded. This was the case with cattle that were genetically modified in 2015/2016 to make them hornless. It was only in 2019 that scientists found genetic material from the bacteria used in the process had also been introduced into the genetic material of the cattle. Amongst others, they found complete DNA-fragments able to confer resistance to antibiotics in the genomes. Luckily these animals had not been used for commercial breeding, otherwise these undesirable genetic changes could have spread rapidly and widely within the populations.

This example shows: The differences between naturally occurring processes (or conventional breeding) and NGTs may be easily overlooked but can, nevertheless, have serious consequences. If these unintended effects are overlooked, they may spread rapidly within large populations. Therefore, New GE organisms have to be examined thoroughly for unintended genetic changes.

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Further information: 
Source: Norris et al. (2020) Template plasmid integration in germline genome-edited cattle, Nature Biotechnology

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