Transgenic Mouse as Tools for the Study of Congenital Anomalies *

The molecular events that guide pattern formation during embryonic development have been difficult to characterize in mammals, partly because of the difficulty in drawing a molecular connection between the phenotype of a dysmorphic mutation and the specific gene in which that mutation occurs. However, recent advances for recombinant DNA technique have made it possible to approach and clone the genes involved in the developmental process. The experimental insertion of retroviral or molecularly cloned DNA into mouse embryos to produce transgenic mice is one such approach that has led to information on phenotypes of dysmorphic mutation at the molecular level. During a series of transgenic experiment weobtained a developmental mutant that showed an autosomal dominant trait characterized by a short snout. The primary couse of this dys‐morphism was a developmental defect in the first branchial arch. The transgene was integrated into the chromosome 13. One fragment flanking the insertion site was highly conserved in mammals.