Mean distortion product otoacoustic emissions in isogenic Beethoven mice. DP-grams for (A) isogenic Tmc1+/+ (C3H-+/+), Tmc1Bth/+ (C3H-Bth/+), and Tmc1Bth/Bth (C3H-Bth/Bth) mice at 4 weeks of age; (B) Tmc1Bth/+ (C3H-Bth/+) at 4, 8, 12, and 32 weeks of age; (C) Tmc1Bth/Bth (C3H-Bth/Bth) at 4 and 12 weeks of age; (D) Tmc1+/+ (C3H-+/+) at 4, 8, 12, and 32 weeks of age. Vertical bars indicate standard deviations. Data were included for both ears of each animal.