 Molecular technologies changed the way research was done in molecular biology. In vitro systems that helped among other things to solve the genetic code, were complemented by new methods of in vivo manipulation and detection (Rheinberger 2009). This in turn led to the discovery of new cellular mechanisms involved in the transcription and translation of genes. For instance, it had been observed in virus-based model systems that in some cases mRNA corresponded to non-contiguous fragments of the DNA from which it was transcribed. Further studies revealed that in these cases parts of the initial transcript were removed to form the mature mRNA that was eventually translated and the segments that were removed could separate coding regions. Much to the surprise of biologists, this was the case for all genes in eukaryotic cells, while the mechanism was absent in prokaryotes (Abir-Am 2020; Morange 2020: Ch. 17). “Split genes” and the mechanism of RNA splicing led to an important reconception of genes. As Walter Gilbert (born 1932) wrote: