Why is pink colour produced in a heterozygote snapdragon ? I'm seeking explanation at a molecular level. Thank you.
The dominant allele A encodes for the enzyme required for the production of red anthocyanin, which is stored in the vacuole of the plant petal cells. The recessive allele a does not encode for the functional enzyme, thus red pigment is not produced and homozygous plants remain white. However, now lest compare the color of AA and Aa plant. In case of AA plant both alleles result in the functional enzyme, while in case of Aa plant only one allele. It means that cells of AA plant can produce twice more enzyme and red pigment than cells of Aa plant. In AA plant the red pigment is more concentrated and their petals look red. In case of Aa plant the pigment is dilute and the petals are pink. You can observe it diluting different amounts of red paint in the same volume of water. The intensity of color will be different.