Generalize: If either allele is the(dominant, recessive) allele for a trait, the organism will exhibit that trait. An organism will express the recessive trait only when(no alleles are, one allele is, both alleles are) recessive

Mendel’s law of dominance states that the dominant allele is always expressed. For example if there were two homozygous rats, one with grey fur, GG and one with white fur gg, the F2 generation will have Gg, expressing the dominant grey fur, only when having gg, two recessive alleles, will the recessive Gene be exhibited. Therefore only when both alleles are recessive.