Two new mutant genes in the house mouse

Summary

1. Fidget is a new recessive gene with regular manifestation and nearly normal viability under laboratory conditions. Affected animals shake their heads in the horizontal plane and often run in circles. A period of hypersensitivity to sounds early in life is followed by deafness or a condition approximating deafness. Lesions of the cornea are regularly found. Polydactylism of the hind feet was observed in fifteen out of eighty-six fidgets; its rare occurrence in normal segregants may be due to occasional semi-dominance of this trait. Fidget males usually breed well, while fidget females are unreliable mothers.

2. Hydrocephalus-3 is a recessive gene which overlaps normal if classification is based on living animals. The onset of clinical signs is usually early in the second week, but occasionally much later. Heavily affected animals are greatly retarded in development and rarely reach the age of two months. A feature of hydrocephalic young is nasal discharge, which is also found in mild cases, which have no recognizable skull anomaly, though they are retarded in development. Such young often survive to reach full adult size; whether they may become sexually functional is unknown. The genetic relations ofhy-3 tohy-1 andhy-2 remain to be cleared up by crosses.