Models and diagrams as thinking tools: the case of satellite-DNA

The aim of the paper is to present some ideas on the transition between the material representations of phenomena in experimental systems, commonly referred as material traces or inscriptions (for instance, in an electrophoretic gel or a paper chromatography), and the more "public" and "general" representations of phenomena (including tables, diagrams, graphs and other visual and textual representations). To do so, the story of the early representations of satellite-DNA, a fraction of about 400 base-pair-long repeated sequences in eukaryotic DNA stabilized in the mid 1960s, will be presented. The author argues that the practices associated to different moments of research (such as the stabilization of phenomena, the reconstruction of a process, the modeling of mechanisms or the communication of results, among others) require the construction and the translocation of meanings between different ways of representing. Special attention is given to a kind of scientific diagram used in experimental tradition to understand processes and mechanisms; following Dewey's conception of tools these diagrams are called "thinking tools".