The six-fingered gene dominates the five-fingered gene, in a family where one parent is five-fingered

The six-fingered gene dominates the five-fingered gene, in a family where one parent is five-fingered, the other six-fingered, a child with a normal hand structure was born. Can we expect the next child with a normal hand?

Let’s designate the gene responsible for the six-fingered hand as “A”, then the gene that determines the development of a normal five-fingered hand will be designated as “a”.

The five-toed parent carries the recessive genotype aa, because homozygosity is a condition under which a recessive trait acquires the ability to be realized in the phenotype. This parent produces a-type germ cells.

A child born with a normal hand is also aa. Since he inherited a normal gene from each of the parents, we can conclude that the six-fingered parent is heterozygous for the number of fingers of the hand – Aa. It produces germ cells A and a.

Variants of the offspring of such parents:

children with a normal hand aa – 50%;

six-toed children Aa – 50%.

Answer: the probability of a given pair of giving birth to a child with a normal hand is 50%.