Early in the origin of life, as it is presently conceived, there was no distinction between genotype and phenotype. What characterizes this distinction, and at what stage of organization may it be said to have come into being
Genotype refers to the genetic make-up of an organism while phenotype refers to the physical appearance of an organism.
What characterized the distinction between genotype and phenotype was the discovery of the gene as a dictator of physical appearance. In order words, the distinction between genotype and phenotype was made possible only when gene and self-replicating DNA were discovered and the fact that the gene is a factor that determines how organisms look.
