The spouses, who were deaf from birth, had a normal hearing child. What genetic phenomenon can explain this, if the genotype

The spouses, who were deaf from birth, had a normal hearing child. What genetic phenomenon can explain this, if the genotype of the woman is Aabb, and the genotype of the man is aaBb? What is the likelihood of this baby being born deaf and dumb?

Most likely, deafness in this task is due to homozygosity for one of a pair of recessive genes. That is, there are two types of deafness, one of which develops in the case of homozygosity for the b gene, the second – for the a gene.

Since in the genotypes of both parents there are dominant genes A and B, which suppress the development of deafness in the case of heterozygosity, that is, the probability of having a child with a genotype corresponding to the normal hearing – AaBb.

The mother, according to the condition, Aabb, produces eggs Ab and ab.

Father – aaBb, produces spermatozoa aB and ab.

Children born to this couple will be represented by the following options:

with normal hearing (AaBb) – probability 25%;

deaf according to one of the forms of genetic deafness (aaBb or Aabb) – 50%;

deaf for both forms of deafness (aabb) – 25% probability.

Answer: This couple has a 75% chance of having a child with deaf-dumbness. The birth of a normally hearing child is explained by the independent inheritance of genes that make up a particular allele.