GENE AND CHROMOSOME MUTATIONS 239 



dominant in the presence of one W" j^ene. Dunn and Thi^pen, kj.^i, ). 

 Hered. 21 : 495 498. 



si shaker short. — Recognizable at birth by absence or reduction of the 

 tail and by the presence of one or two small blood-blebs in the dorsal median 

 line of the head. Disturbances of equilibrium suggestive of shaker- 1 appear 

 at about 5 days. Semicircular canals and endolymphatic appendage are 

 lacking, and the cochlea and cortical organ are abnormal. Deaf. Sterile 

 in both sexes. Bonnevie, 1936, Genetica 18: 105-125. 



/ type allele of T. 



T brachyury. — Tt mice are short-tailed (brachyuric). TT gives abnor- 

 mal embryos which die about 11 days after fertilization. Dobrovolskaia- 

 Zavadskaia and KoboziefT, 1934, Arch. zool. exp. et gen. 76: 249 358. 



/° lethal allele of t. — Tt^ mice are tailless; /"/" gives abnormal embryos 

 which stop developing at between 53^-^ and 7 days embryo age; tt^ mice are 

 normal. Males heterozygous for t^ and either T or / transmit t^ to more 

 than half their progeny, probably due to an efTect of t'^ on segregation. 

 Gluecksohn-Schoenheimer, 1940, Genetics 25: 391-400. 



t^ lethal allele of t. — Tt^ mice are tailless; t^t^ mice die before implanta- 

 tion; t^t^ males are sterile, the females normal. Like t^ in its effect on ratios. 

 Dunn and Gluecksohn-Schoenheimer, 1939, Genetics 24: 587-609. 



T^ fused. — Allele of /. TH mice usually have a kinked tail due to fusion 

 of vertebrae, but there are normal overlaps in some stocks. T^T^ mice 

 show a more marked expression of the same trait, the tail often being very 

 short. Reed, 1937, Genetics 22: 1-13. 



V waltzing. — Shaking movements of the head and a tendency to run in 

 circles. Deaf. Probably due to a defect of the inner ear. Not always dis- 

 tuinguishable phenotypically from sh-i and sh-2. Gates, 1926, Carnegie 

 Instn. Wash. Pub. No. 337: 83-138. 



w type allele of W. 



W dominant spotting. — WW mice are anaemic, usually living for only 

 a few days after birth. Those surviving long enough to develop a coat are 

 all white with black eyes. In the presence of certain recessive modifying 

 genes, m{w), at least 3 in number, W is partly dominant, Ww mice showing 

 90-98% white. In the absence of the modifiers, Ww mice show no spotting; 

 with only some of the modifiers present, the degree of spotting is inter- 

 mediate. One dose of 5 increases the spotting in Ww mice provided some 

 or all of the modifiers are present. A" tends to reduce the amount of white 

 spotting. Dunn, 1937, Genetics 22: 43-64. Dunn, MacDowell and 

 Lebedeff, 1937, Genetics 22: 307-318. 



