In a species of flowering plant, the synthesis of a red anthocyanin pigment requires the cooperative action of two independent enzymes encoded by genes A A\,A and BBB. A plant must possess at least one dominant allele of both genes (A A\,A and BBB) to produce red flowers; all other genotypes result in white flowers.
How is a plant with the genotype Aabb Aabb\,Aabb described genetically, and what is its flower phenotype?
Heterozygous at the first locus and homozygous recessive at the second locus; red flowers.
Heterozygous at the first locus and homozygous recessive at the second locus; white flowers.
Homozygous dominant at the first locus and heterozygous at the second locus; white flowers.
Homozygous recessive at the first locus and heterozygous at the second locus; white flowers.