Answer: The father's phenotype is non- roller and his genotype is rr. The mother's phenotype is tongue-roller and her genotype is Rr because she is a heterozygous tongue-roller.
The probability of having a child who is a tongue-roller is 1/2 and the probability of having a non-roller child is 1/2.
Explanation: The possible genotypes of their children are Rr and rr. Fifty percent of the children are tongue-rollers while fifty percent are non-rollers. Children with Rr genotype will manifest outwardly as tongue-rollers because being a tongue-roller R is dominant over being a non-roller r. R is dominant over r.
See the attached punnet square for better understanding.
