Fig. 1.

Frequency distribution of auditory-evoked brainstem response (ABR) thresholds in (A/J×CAST/Ei)×A/J backcross progeny. Hearing loss occurs earlier in NOD/LtJ and SKH2/J backcross mice than in A/J backcross mice, but otherwise their ABR threshold frequency distributions are similar. Mice were tested successively at ages 3 months (light bars) and 6 months (dark bars). The vertical dashed line indicates division between normal and elevated ABR thresholds. Backcross matings were set up using males and females from both types of reciprocal F₁ hybrid. Maternal strain origins in N2 backcross mice were noted.