Answer
Individual 1 would be either heterozygous, or homozygous with the normal allele. Individual 2 would have homozygous recessive, meaning that individual 2 is deaf. Individual 3 is heterozygous. Individual 4 is homozygous normal.
Work Step by Step
Individual 1 is homozygous normal or heterozygous because the offspring of individual 1 and 2 do not carry the mutation. Individual 2 carries the mutation, and as the mutation is recessive, individual 2 must be homozygous recessive. We know that Individual 3 is heterozygous and 4 is homozygous normal, because their offspring do not carry the mutation until they mate as well.
