a1 M.R.C. Radiobiological Research Unit, Harwell, Berkshire
Curtailed (Tc) 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. Tc 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 Tc 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, Tc and Th are discussed.
(Received February 11 1965)