Question

In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller marries a woman who is heterozygous for tongue rolling.
Father’s phenotype _______ Father’s genotype ______
Mother’s phenotype ________ Mother’s genotype _______

What is the probability of this couple having a child who is a tongue roller? Show your answers by drawing a Punnett’s square.

Answer 1

Answer:

Father’s phenotype non roller Father’s genotype rr

Mother’s phenotype roller Mother’s genotype Rr

Probability of this couple having a child who is a tongue roller : 1/2

Explanation:

Given that allele for rolling (R) is dominant over allele for non rolling (r).

Since father is a non roller his genotype would be rr

Mother is a heterozygous tongue roller so her genotype would be Rr

Their progeny:

Rr  X   rr  :

   R     r

r  Rr   rr

r  Rr   rr

Half of the offspring have Rr genotype which will make them tongue roller so probability of this couple having a child who is a tongue roller is 1/2.