For decades scientists have been perplexed by different circumstances surrounding families with rare, early-onset auditory neuropathy (deafness). In some families, parents and grandparents of the proband have normal hearing, while in other families, a number of affected (deaf) family members are scattered throughout the pedigree, appearing in every generation.

Required:
Assuming a genetic cause for each case, offer a reasonable explanation for the genetic origin of such deafness in the two types of families.