If one parent has two dominant alleles for tongue-rolling and the other has two recessive alleles, what percentage of their children will be able to roll their tongue?

If one parent has two dominant alleles for tongue-rolling and the other has two recessive alleles, what percentage of their children will be able to roll their tongue?

• A. 0%
• B. 25%
• C. 50%
• D. 100%

Answer: (D)

Tongue-rolling is a dominant trait, so having at least one dominant allele will express the ability to roll the tongue. When one parent has two dominant alleles and the other has two recessive alleles, every child receives one dominant allele from the first parent and one recessive allele from the second. That means all offspring have a dominant allele, resulting in the ability to roll the tongue for every child. Therefore, 100 percent of the children can roll their tongues.

Tongue-rolling is a dominant trait, so having at least one dominant allele will express the ability to roll the tongue. When one parent has two dominant alleles and the other has two recessive alleles, every child receives one dominant allele from the first parent and one recessive allele from the second. That means all offspring have a dominant allele, resulting in the ability to roll the tongue for every child. Therefore, 100 percent of the children can roll their tongues.