Some people can roll their tongue into a tube shape, while other cannot. Practicing is not likely to help because tongue-rolling is an inherited trait. The allele for rolling the tongue (R) is dominant to the allele for not being able to roll the tongue (r). Look at the Punnett square. It shows a cross between two parents with at least one R allele. Complete the Punnett square above by identifying the correct locations (letter) for each allele and genotype (pair of alleles).
C


A


B


D

1.
R

2.
RR

3.
r

4.
Rr

5.
rr