4.
If the offspring of a dihybrid cross have a 9:3:3:1 phenotypic ratio, what must be true of the parents’ genotypes?
Both parents are heterozygous for only one trait.
Both parents express the dominant trait.
Both parents express the recessive trait.
Both parents are heterozygous for both traits.
If the offspring of a dihybrid cross have a 9:3:3:1 phenotypic ratio, what must be true of the parents’ genotypes?
Both parents are heterozygous for only one trait.
Both parents express the dominant trait.
Both parents express the recessive trait.
Both parents are heterozygous for both traits.