Question

Which molecule is directly responsible for the phenotype of an organism?

Answer 1

The proteins are directly responsible for the phenotype of an organism.

Explanation:

The proteins for eye color for example are different for different colors of eyes. Skin color depends on the number of proteins in skin for making melamine. Even white skinned people will produce more melamine in response to exposure to sunlight producing more proteins.

The production of proteins is controlled by the DNA which sends out mRNA to instruct the ribosomes RNA to make the proteins. So ultimately it is the DNA that controls the phenotype indirectly through the RNA and protein production. But proteins are directly responsible for the phenotype.