Extra-toes: anew mutant gene causing multiple abnormalities in the mouse.

Abstract

The present paper deals with the genetics, morphology and developmental anatomy of a new mutant gene in the mouse called extra-toes. Extra-toes (symbol Xt ) derives its name from the fact that in the heterozygous condition there are extra digits on the preaxial side of both hind feet. Apart from this (and corresponding changes in the forefeet) heterozygotes are externally normal. The homozygote dies at birth or in utero with a wide range of abnormalities. These include oedema, paddle-shaped feet with up to eight digits, hemimelia and gross malformations of the brain, central nervous system and sense organs. Extra-toes arose in the control series of an irradiation experiment at the M.R.C. Radiobiological Research Unit at Harwell. Five Xt /+♂♂ and two Xt /+♀♀ were sent to the Animal Genetics Department at University College London in November 1962. Two of the ♂♂ were mated with the ♀♀, and the remaining three with ♀♀ from the CB stock (the F1 of CBA/Gr and C57BL/Gr). An Xt /+♂ was outcrossed to two CB ♀♀ in November 1963. With these exceptions the stock has been brother/sister mated throughout.