Biological Process Annotation Data. This figure is reproduced from Washington Smoak et al . The figure shows micrographs of hearts in 16.5dpc mouse embryos. The figure on the left shows an animal with two functional copies of the Shh gene and the figure on the right shows an animal with no functional copies. Ao and Pa indicate the aorta and the pulmonary artery respectively. The ? indicates an aberrant outflow tract. Reprinted from Developmental Biology, 283, Washington Smoak et al, Sonic hedgehog is required for cardiac outflow tract and neural crest development, 357-72, Copyright 2005, with permission from Elsevier.