While genetic dominance — defined as any deviation from a purely additive, or dosage, effect of a genotype on a trait — is well-documented in plant and animal breeding, its existence in humans is limited aside from rare monogenic traits. In a new study, researchers from the Broad Institute and Massachusetts General Hospital analyzed common genetic variation across roughly 1,000 traits, including a number related to human disease, across more than 361,000 participants in the UK Biobank. As they report this week in Science, they then developed a computational method to rapidly estimate the dominance contribution to phenotypic variance across thousands of phenotypes. Overall, the investigators find a modest number of individually significant loci and broadly confirm that heritability explained by dominance is small, matching the findings of previous analyses.