Question

Given the information below, answer the following questions, assuming complete dominance. Tongue rolling is a dominant trait. If two individuals homozygous dominant for this trait have a child, what is the chance that the child will not be able to roll his tongue?

Answer 1

Answer:

The chance that their child will not be able to roll his tongue will be zero.

The chances to have a child with tongue rolling ability is 100%.

Explanation:

In complete dominance, a dominant gene completely manifests over a recessive gene. If tongue rolling is a dominant trait, this means that the gene that expresses this trait is dominant over the recessive one that does not allow the person to roll the tongue.  

If the gene for tongue rolling is called T, then a person that is homozygous dominant for this trait will have the following genotype: TT. If the person is heterozygous for this trait, the genotype will be Tt. And if a person is homozygous recessive for the trait, this person´s genotype will be tt.

When two homozygous dominant individuals mate, their chances to have a child with tongue rolling ability is 100%.

This is:    

Parental)         TT   x   TT

Gametes)     T   T       T   T

Punnet Square)                  T                 T

                                T        TT             TT

                                T        TT             TT

F1)  Genotype: 100% TT, or 4/4 TT

      Phenotype: 100% Tongue rolling capable.

Answer 2

In complete dominance, a dominant gene completely manifests over a recessive gene. If tongue rolling is a dominant trait, this means that the gene that expresses this trait is dominant over the recessive one that does not allow the person to roll the tongue.   If the gene for tongue rolling is called T, then a person that is homozygous dominant for this trait will have the following genotype: TT. If the person is heterozygous for this trait, the genotype will be Tt. And if a person is homozygous recessive for the trait, this person´s genotype will be tt. When two homozygous dominant individuals mate, their chances to have a child with tongue rolling ability is 100%. This is:    Parental)         TT   x   TTGametes)     T   T       T   TPunnet Square)                  T                 T                                 T        TT             TT                                 T        TT             TTF1)  Genotype: 100% TT, or 4/4 TT       Phenotype: 100% Tongue rolling capable.