1 Tim King and Nigel A. Brown, MRC Experimental Embryology and Teratology Unit, and Department of Child Health, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
The origin of left-right asymmetry during vertebrate embryogenesis has long been a puzzle; now, for the first time, genes have been identified that are expressed with left-right asymmetric patterns in early embryos.