Consider a dihybrid cross between two true-breeding parents in which the two genes under investigation exhibit a simple Mendelian dominance/recessive relationship and assort independently from one another during meiosis (i.e. are unlinked).
One parent is homozygous dominant for both loci (e.g. AaBb), while the second parent is homozygous recessive for both loci (e.g. aabb).
What is the expected phenotype ratio in the resulting F1 generation?