A consortium of scientists from Yale and EMBL, among others, used high-resolution analysis to study the genetics of Down syndrome in a paper published in the early online edition of PNAS this week. The scientists created a genetic map for 30 patients with rare segmental trisomies of various regions of HSA21 and found regions of 1.8 Mb -16.3 Mb likely to be involved in the development of eight of the cases, confirming the role of a single consensus region in causing severe Down syndrome.