Feather color in parakeets is produced by the blending of pigments from two biosynthetic pathways shown below. Four independently assorting genes (A, B, C, and D) produce enzymes that catalyze separate steps of the pathways. For the questions below, use an uppercase letter to indicate a dominant allele producing full enzymatic activity and a lowercase letter to indicate a recessive allele producing no functional enzyme. Feather colors produced by mixing pigments are green (yellow + blue) and purple (red + blue). Red, yellow, and blue feathers result from production of one colored pigment, and white results from absence of pigment production.
If F₁ birds identified in part (c) are mated at random, what phenotypes do you expect in the F₂ generation? What are the ratios among phenotypes? Show your work.