Genetical studies on the skeleton of the mouse xvi. Tail-kinks

Summary

• 1. Tail-kinks (tk/tk) in the mouse is clue to a simple autosomal recessive gene with regular manifestation and full viability under laboratory conditions.

• 2. The major effects of the tail-kinks gene are confined to the axial skeleton. This is grossly affected in the cervical and upper thoracic and again in the caudal region; the intervening region is almost normal. Ribs are often involved and the manubrium sterol is usually fused to the next sternebra.

• 3. The distribution of abnormalities over the vertebral column is such that the small vertebrae at both ends are severely affected while the large ones in the middle are almost immune.

• 4. The abnormalities of the osseous skeleton are preformed in cartilage and are visible to the full extent as soon as chondrification sets in.

• 5. The abnormalities of the cartilaginous skeleton are preceded by defects in the membranous skeleton. These can be traced back to the 10-day stage (C.R..L. 4–5 mm.) when in the normal embryo the cervical sclerotomes have differentiated into anterior and posterior sclerotome halves which differ in tissue density whiletk/tk embryos do not yet show any signs of this differentiation. No differences have been discovered in 9-day embryos (C.R.L. about 3 mm.).