Mendelian disorders and multifactorial traits: the big divide or one for all?

For the past century, Mendelian and multifactorial traits have existed at opposite ends of the disease spectrum in humans. Furthermore, the recent emphasis on genome-wide association studies for uncovering variants that underlie common diseases has risked deepening the divide - or has it? Four experienced human geneticists express their views on the changing landscape of human disease studies and the impact of new technologies and study designs on the age-old aim of connecting a genomic variant with its phenotypic consequences.