The relationship between axon diameter and myelin thickness is normal in dnβ1 mice. (a) Representative electron micrographs of sections of optic nerve, spinal cord, and cerebellum of P28 wild-type and dnβ1 mutant mice. Bar: 1 µm. (b) The linear regression of the g-ratio measurements for each animal (n = 3) is shown for the three CNS areas. Solid and dashed lines represent wild-type and mutant animals, respectively. (c) Scatter plot displays g-ratios of individual myelinated axons (obtained from three animals) as a function of the respective axon size. Closed and open circles represent wild-type and mutant axons, respectively.