Not functional yet a difference maker: junk DNA as a case study

Abstract

AbstractIt is often thought that non-junk or coding DNA is more significant than other cellular elements, including so-called junk DNA. This is for two main reasons: (1) because coding DNA is often targeted by historical or current selection, it is consideredfunctionallyspecial and (2) because its mode of action is uniquely specific amongst the other actual difference makers in the cell, it is consideredcausallyspecial. Here, we challenge both these presumptions. With respect to function, we argue that there is previously unappreciated reason to think that junk DNA is significant, since it can alter the cellular environment, and those alterations can influence how organism-level selection operates. With respect to causality, we argue that there is again reason to think that junk DNA is significant, since it too (like coding DNA) is remarkably causally specific (in Waters’, in J Philos 104:551–579, 2007 sense). As a result, something is missing from the received view of significance in molecular biology—a view which emphasizes specificity and neglects something we term ‘reach’. With the special case of junk DNA in mind, we explore how to model and understand the causal specificity, reach, and correspondingefficacyof difference makers in biology. The account contains implications for how evolution shapes the genome, as well as advances our understanding of multi-level selection.