In Oompa Loompas, gray face (G) is dominant to orange recessive face (g). If two gray faced Oompas have an offspring with an orange face, what must the genotype for each of the parents?

The genotype for each of the parents must be

parent 1 : Gg

parent 2 : Gg

Explanation:

Please note that a dominant trait is a trait that is expressed phenotypically in a heterozygous state, while a recessive trait is a trait that can only be expressed in a homozygous state.

Now, since gray face (G) for Oompa Loompas is dominant, and orange face (g) is recessive, for an offspring to be orange faced, it means that the genotype of the offspring must be 'gg'. Also, since both parent contribute an allele in the pair of alleles in the offspring, both parents must have the recessive (g) in their genotype. Moreover, we are told that both parents are gray-faced, meaning that their genotypes were 'Gg' and 'Gg'. To confirm, let me do the cross

                                 G           g

G                                GG       Gg

g                                 Gg        gg

from the cross above, we find out that out of 4 offspring, 3 were gray face (GG, Gg ) while one was orange face (gg).