In a diploid plant species, the biosynthesis of purple anthocyanin pigment from a colourless precursor is controlled by two unlinked genes, D D\,D and EEE, according to the pathway shown below:
- Dominant allele D D\,D codes for active Enzyme D; recessive allele d d\,d codes for an inactive enzyme.
- Dominant allele E E\,E codes for active Enzyme E; recessive allele e e\,e codes for an inactive enzyme.
- If either enzyme is inactive, the pathway is blocked at that step.
Two plants, both heterozygous for both genes (DdEeDdEeDdEe), are crossed. What is the expected phenotypic ratio of their offspring?
9 Purple:3 Red:4 Colourless9\text{ Purple} : 3\text{ Red} : 4\text{ Colourless}9 Purple:3 Red:4 Colourless
9 Purple:7 Colourless9\text{ Purple} : 7\text{ Colourless}9 Purple:7 Colourless
12 Purple:3 Red:1 Colourless12\text{ Purple} : 3\text{ Red} : 1\text{ Colourless}12 Purple:3 Red:1 Colourless
9 Purple:3 Red:3 Pink:1 Colourless9\text{ Purple} : 3\text{ Red} : 3\text{ Pink} : 1\text{ Colourless}9 Purple:3 Red:3 Pink:1 Colourless