Phenotype and hearing sensitivity of mtl and bsd adult mice. A

, Dorsal views show the different body size and tail lengths of wildtype and homozygotes. Ventral views show the presence of white belly patches of variable size in mtl and bsd homozygotes. B, Mean ABR thresholds (± standard deviation) plots for mtl/mtl compared to +/+ tested at 6–7 weeks of age (upper panel) and plots showing the mean ABR thresholds of mice with genotypes +/+, +/bsd and bsd/bsd around 6 weeks of age (lower panel). Clicks and tones were presented up to 95 dB SPL; all mutants showed no detectable ABR at even the highest sound level presented (these values are indicated by the arrows). The absence of discernible ABR at 95 dB SPL suggests a profound hearing loss.