Curtailed, a new dominant T-allele in the house mouse

Curtailed ( T c ) is a new T-allele which leads to complete or near-complete absence of the tail in heterozygotes, apart from a small caudal filament. Other heterozygous defects include absence of the axis odontoid process and of the nuclei pulposi, a tendency to have rib and vertebral fusions and a slight decrease in the average number of presacral vertebrae. T c is lethal when homozygous, causing similar but more extreme defects than T , with absence of all limb-buds and non-closure of the neural folds. A comparison of T c with other mutants suggests that the anomalies are mainly the result of more severe effects on the notochord-mesoderm system than in T . Differences between the genetic behaviour of T , T c and T h are discussed.