In humans, deaf-mute is inherited as an autosomal recessive trait, and normal hearing is inherited

In humans, deaf-mute is inherited as an autosomal recessive trait, and normal hearing is inherited as autosomal dominant. Determine the likelihood of a deaf-mute child being born to a deaf-mute mother.

Let’s designate the gene responsible for the development of deaf-dumbness as g, then the gene corresponding to normal hearing will be G.

A deaf-mute woman will be gg, since the homozygosity of her genotype is an obligatory condition for the phenotypic realization of a trait that is recessive.

It produces oocytes of the same type g and transmits only information about deaf-mute to the offspring.

A hypothetical deaf-mute child must also be gg, for this he must inherit the second gene g from his father.

A man can produce g-type spermatozoa in two cases: either he is Gg, which corresponds to normal hearing, then 50% of the offspring of such a pair will be deaf and dumb; or he himself is deaf and dumb – gg: all children of such a couple will be deaf and dumb.

If the father can hear normally and has a homozygous genotype for the normal hearing gene, GG, then all offspring of the couple will hear.

Answer: the probability of having a deaf-mute child in a deaf-mute mother depends on the genotypic variant of her husband, the child’s father and ranges from 0% (if the father is GG) to 100% (if the father is deaf-mute, that is, gg).