Idiomatic (gene) expressions.

Hidden among the myriad nucleotide variants that constitute each species' gene pool are a few variants that contribute to phenotypic variation. Many of these differences that make a difference are non-coding cis-regulatory variants, which, unlike coding variants, can only be identified through laborious experimental analysis. Recently, Cowles et al.1 described a screening method that does an end-run around this problem by searching for genes whose cis regulation varies without having to find the polymorphic nucleotides that influence transcription. While we will continue to require a diverse arsenal of experimental methods, this versatile method will speed the identification of functional genetic variation.