Question

In humans, tongue rolling is a dominant trait, those with the recessive condition cannot roll their tongues. Dave can roll his tongue, but his father could not. He is married to Nancy, who can roll her tongue, but her mother could not. What is the probability that their first born child will be able to roll his tongue

Answer 1

0.75 or 75%

Explanation:

Let R be the dominant allele for rolling the tongue and r be the recessive allele for not rolling the tongue. If both Dave and Nancy can roll their tongues and had a parent that could not, they both have a heterozygous genotype (Rr).

The sample space for the genotype of their first born child is:

S={RR, Rr, rR, rr}

Only the homozygous recessive genotype rr makes it so that their child is not able to roll his tongue. Therefore, the probability that their first born child will be able to roll his tongue is:

`P=(3)/(4)=0.75=75\%`