Question

The ability to roll your tongue is determined by a dominant gene (R) while recessive gene results in the inability to roll the tongue (r). A man and his wife can both roll their tongues and are surprised to find that thier son cannot. Explain this by showing the genotypes of all three persons

Answer 1

The genotypes of the parents would both be Aa or heterogeneous. Therefore, based on a punnet square, there is a 25% chance that the offspring would have the genotype aa or homogeneous recessive, which occurred.