 No concept is more central to genetics than the “gene”. And yet, the earliest philosophical examinations of genetics quickly uncovered the fact that it was by no means clear that the gene from classical genetics was the same thing as the gene from molecular genetics. Subsequent attention to genetics only compounded the puzzle. In the late 1970s, a series of discoveries complicated the simple relationship between a single, uninterrupted sequence of DNA and its polypeptide, protein product. Overlapping genes were discovered (Barrell et al. 1976); such genes were considered overlapping because two different amino acid chains might be read from the same stretch of nucleic acids by starting from different points on the DNA sequence. And split genes were found (Berget et al. 1977; Chow et al. 1977). In contrast to the hypothesis that a continuous nucleic acid sequence generated an amino acid chain, it became apparent that stretches of DNA were often split between coding regions (exons) and non-coding regions (introns). The distinction between exons and introns became even more complicated when alternative splicing was discovered the following year (Berk and Sharp 1978). A series of exons could be spliced together in a variety of ways, thus generating a variety of molecular products. Discoveries such as overlapping genes, split genes, and alternative splicing made it clear that what counted as a gene was by no means straightforward even if focus was confined to molecular genetics (Griffiths and Stotz 2013; Rheinberger and Müller-Wille 2017; entry:  molecular biology).