Audiogram — Cookie-Bite Mid-Frequency Genetic SNHL

A 6-year-old child is brought to the ENT clinic with complaints of difficulty understanding speech, especially in noisy classroom environments. Pure-tone audiometry shows a distinctive U-shaped loss centered at 1–2 kHz, with normal thresholds at 250–500 Hz and 4–8 kHz. The structure marked **A** in the audiogram represents this mid-frequency cookie-bite configuration. Tympanometry is normal (type A), and acoustic reflexes are present. The child's father has a similar hearing loss pattern. Which of the following is the most likely genetic basis for this hearing loss?