Question

The ability to roll the tongue (R) is determined by a dominant gene while the 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 their son cannot. Explain this by showing the genotypes of all three persons.

Answer 1

Both of the parents were heterozygous (Rr) for rolling their tongues where as their child inherited the recessive (r) from both parents and was (rr) he was in the 25% chance that would happen. The punnet square tells us there's a 25% chance the kid would be RR 50% Rr and 25% rr

Answer 2

These are the possible genotypes RR, Rr, Rr, rr First 3 carries dominant gene for tongue rolling, so they can do it, while the 4th genotype rr is homologous for recessive, and he/she can't perform tongue rolling.