Why don’t all phenotypic traits occur as discrete, alternative states like Mendel’s peas?. Earth & Marine Sciences

Phenotypic traits are rarely determined by single Mendelian loci. Variation in some traits can be attributed to the cumulative action of many genes, but the environment can also influence phenotypic traits. Variation in the environment can lead to variation in the phenotypes that arise from a single genotype, as do the complex interactions between many different genes and the environment.