Question

John can roll his tongue and is heterozygous for this dominant trait (Rr). John’s second toe is shorter than his first. His wife Rita cannot roll her tongue and has a longer second toe. Rita is heterozygous for this dominant trait (Tt). Use a Punnett square to predict the possible genotype(s) and phenotype(s) of their first child?

Answer 1

The Punnett square predicts that John and Rita's child has a 50% chance of inheriting the ability to roll their tongue and a 50% chance of having a longer second toe, as well as the respective opposite traits.

Step-by-step explanation:

John has the genotype Rr for the ability to roll his tongue, which is a dominant trait. Rita cannot roll her tongue and thus has the genotype rr. For the second trait of toe length, John is recessive (presumably tt since his second toe is shorter than his first), and Rita is heterozygous with genotype Tt. To predict the possible genotypes and phenotypes of their first child for these two traits, we'll use a Punnett square for each trait.

For tongue rolling:

Rr (John) x rr (Rita)

Possible genotypes for their child: 50% Rr (can roll tongue), 50% rr (cannot roll tongue).

For toe length:

tt (John) x Tt (Rita)

Possible genotypes for their child: 50% Tt (longer second toe), 50% tt (shorter second toe).

In summary, the child has a 50% chance of being able to roll their tongue and a 50% chance of having a second toe longer than the first. Likewise, there's a 50% chance the child will not be able to roll their tongue and a 50% chance of having a second toe that's shorter than the first.

Answer 2

rT rt

Rt RrTt Rrtt

rt rrtt rrtt

25% chances for the genotype to be heterozygous roll tongue and heterozygous longer second toe.

25% chances for the genotype to be heterozygous roll tongue and homozygous short toe.

50% chances for the genotype to be homozygous recessive no roll tongue and homozygous recessive short toe.

Phenotypes would be 25% tongue roll with longer toe. 25% tongue roll with shorter toe. 50% no tongue roll,shorter toe.