The biosensing practice concerning us in this chapter bears different names: DNA genotyping, genetic tests or personal genomics. But it targets a single macro-molecule shared by all living things, DNA. DNA genotyping begins with a tissue sample, usually taken from saliva. Where it ends is difficult to say. Since 2007, DNA genotyping has been available ‘direct’ to ‘consumers’. In this context, ‘direct’ means without recourse to a medical clinic or medical pathology services. The tests, sometimes called ‘direct-to-consumer’ (DTC) genetic tests, are direct in the sense that people submit their saliva and payment from home rather than at a doctor's clinic or medical facility, and results come back to them rather than to a physician. In many respects, the tests are indirect. They depend on social network platforms, they leverage publicly funded scientific research and they struggle to comprehend and capitalise on test results whose significance snakes around plural variations of patterns of DNA. They are steeped in practices and patterns of biomedical and Internet platformisation that precede and expand beyond them. The genotyping platforms, with their devices – for example, DNA chips or microarrays – and scientific entourage (genome-wide association studies [GWAS], DNA genotyping data and literature databases, and so on) – build on wider transformations in biology, life sciences and biomedicine. They are rooted in the exigencies of institutional health care, online platforms and the changing relations of states to their citizens. DNA genotyping platforms – our preferred term for the biosensing dimension of DTC genetic tests – display all the messy entanglements of selfhood, relatedness, regulation, health, science, technology, platform capitalism and collective sense-making visible in biosensing more widely.

This chapter describes some key aspects of the burgeoning of DNA biosensing, bringing into focus its attachment to Internet platforms, ambivalence towards clinical expertise, speculation on future scientific knowledge and embrace of ‘data citizenship’. In terms of biosensing practices and the life course, DNA genotyping ostensibly concerns the problem of future risks or susceptibilities (for example, of Alzheimer's disease or macular degeneration), some or many of which endure beyond the course of an individual life. However, as we will suggest, DNA biosensing stretches above and beyond risk calculations or predictions of individual health outcomes.