||Recombinant DNA technology has provided the tools to modify the genome of an animal, either by
knocking out genes (knock-out) or by inserting new genes (knock-in) that are linked to specific pathways or diseases. Genetic modification has had a major impact on biomedical research, by expanding the range of animal models available, and consequently, by increasing the numbers of animals that are used in research and testing. As a result, the trend of a reduction of experimental animal numbers that was very obvious in the 1970s and 1980s, came to a halt in the early 1990s. The subsequent increase in animal numbers is almost entirely due to the use of genetically-modified
(GM) animals, in both basic and applied research, e.g. in drug development. [...] Thus, studies previously performed in GM mouse lines will be repeated in GM rats and other GM species and, in the end, significantly more GM animal lines will be produced in a wide range of species. Such an increase will definitely be against the European Union policy to move away from the use of animals in biomedical research, as expressed in Council Directive 2010/63/EU.